#Antiviral activity of #tecovirimat against #monkeypox virus clades 1a, 1b, 2a, and 2b

{Excerpt}

The zoonotic Orthopoxvirus monkeypox virus includes two main clades (ie, 1 and 2) relevant to human transmission.1 Two major outbreaks of monkeypox virus have occurred since 2022,1–3 and were declared public health emergencies of international concern by WHO in July, 2022, and August, 2024. The first outbreak was caused by a clade 2b strain that quickly spread worldwide, resulting in approximately 100 000 cases and 200 deaths.3 In the second outbreak, the novel clade 1b emerged.4 As of December, 2024, this upsurge has resulted in more than 55 000 reported or suspected cases and approximately 1000 deaths in DR Congo and neighbouring countries, including Burundi, Rwanda, Uganda, and Angola.4 A few imported clade 1b cases have also been reported in the UK, Sweden, Germany, Belgium, France, the USA, Canada, and Thailand.5 Prevention measures include patient isolation and care as well as vaccines.

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Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00014-3/fulltext?rss=yes

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Characterization of novel highly pathogenic avian #influenza A(#H5N6) clade 2.3.4.4b virus in wild #birds, East #China, 2024

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Dear Editor,

The highly pathogenic avian influenza viruses (HPAIVs) are important epizootic and zoonotic pathogens that cause significant economic losses to the poultry industry and pose a serious risk to veterinary and public health. Wild birds have been recognized as the primary reservoirs for influenza A virus, and some species show little sign of clinical disease or even can be asymptomatic during long distance carriers of the virus (Lycett et al., 2019). Since it was first discovered in 1959, the H5Nx HPAIVs have spread globally and cause outbreaks in wild birds, poultry and sporadic human and other mammalian infections (Lycett et al., 2019). Due to the reassortant events of diverse strains facilitated by migratory waterfowl, the clade 2.3.4.4 of H5Nx viruses acquiring neuraminidase (NA) gene from other low pathogenicity avian influenza viruses (LPAIVs) emerged in 2014 and gradually became the dominant sub-clade (Lee et al., 2017). The genetic diversity of clade 2.3.4.4 of H5Nx hemagglutinin (HA) has further evolved into eight subclades (2.3.4.4a to 2.3.4.4h) according to a unified nomenclature (Graziosi et al., 2024). H5N6 of clades 2.3.4.4d-h were predominantly identified in China from 2014 to early 2020 until the occurrence of a novel H5N6 derived the clade 2.3.4.4b HA gene of H5N8 in December 2020 (Gu et al., 2022). Subsequently, the preponderant clade of the H5N6 subtype HPAIV in China switched into 2.3.4.4b. Recently, novel H5N6 HPAIVs containing HA gene from clade 2.3.4.4b H5N1 virus entered R. O. Korea, with disease outbreaks in poultry and wild bird mortality events (Cho et al., 2024; Heo et al., 2024).

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Source: Virologica Sinica, https://www.sciencedirect.com/science/article/pii/S1995820X25000021?via%3Dihub

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#Receptor #binding, #structure, and #tissue #tropism of #cattle-infecting #H5N1 avian #influenza virus #hemagglutinin

Summary

The ongoing circulation of highly pathogenic avian influenza (HPAI) A (H5N1) viruses, particularly clade 2.3.4.4b strains, poses a significant threat to animal and public health. Recent outbreaks in cattle highlight concerns about cross-species transmission and zoonotic spillover. Here, we found that the hemagglutinin (HA) protein from a cattle-infecting H5N1 virus has acquired slight binding to human-like α2-6-linked receptors while still exhibiting a strong preference for avian-like α2-3-linked sialic acid receptors. Immunohistochemical staining revealed HA binding to bovine pulmonary and mammary tissues, aligning with clinical observations. HA also binds effectively to human conjunctival, tracheal, and mammary tissues, indicating a risk for human transmission, notably in cases of conjunctivitis. High-resolution cryo-electron microscopy (cryo-EM) structures of this H5 HA in complex with either α2-3 or α2-6 receptors elucidate the molecular mechanisms underlying its receptor-binding properties. These findings provide critical insights into the tropism and transmission potential of this emerging pathogen.

Source: Cell, https://www.cell.com/cell/abstract/S0092-8674(25)00048-0

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The sweet side of #H5N1 #influenza virus #infection

Summary

H5Nx viruses remain a threat to human health. Over the past few years, the H5Nx clade 2.3.4.4b has rapidly spread to 6 continents, leading to massive avian and mammalian host deaths. In late March 2024, H5N1 was first identified in lactating dairy cows in the United States and has spread to 16 states, affected hundreds of herds, and caused over 50 known human infections. In this review, we discuss the origins of 2.3.4.4b H5N1 viruses and how they are evolving to better infect mammals, with an emphasis on receptor-binding characteristics. Understanding changes in receptor binding and mutations in the viral genome that allow for sustained spread in mammals can inform public health measures and prevent future influenza virus epidemics and pandemics.

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Source: PLoS Pathogens, https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1012847

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Exotic and #Zoological #Birds Resident and Imported into #Nigeria harbour Highly Pathogenic Avian #Influenza Virus: #Threat to #Poultry Production, Food security and Public Health.

Abstract

Influenza is a major infectious disease challenge affecting animal and human health globally, and wild birds are historically the primary reservoirs of all the known Influenza A virus subtypes. Here, we detected the Highly Pathogenic Avian Influenza (HPAI) virus in exotic and aquatic birds in three different locations in Nigeria. On the 8th of February 2021, exotic birds: Yellow Golden Pheasant (Chrysolophus pictus), Sultan chicken (Gallus gallus domesticus), Lakenvelder chicken (Gallus gallus domesticus), and Common pheasant (Phasianus calchicus), imported from Libya and transported across the Niger Republic border to Nigeria, were presented to the National Veterinary Research Institute, Vom, for screening. Also, a family in Lagos State bought some exotic aquatic birds from a live bird market in Sokoto State, Nigeria, where sudden death was recorded with the birds showing few clinical signs. Similarly, the sudden death of some aquatic birds was reported in Mandela Parks and Gardens in Asaba, Delta State, few weeks after some captured wild birds were introduced to the Park and Gardens. Oropharyngeal, cloacal, and tissue samples were all collected from the reported cases. Total viral nucleic acid was extracted and screened for Influenza A viruses using real-time RT-PCR. The HPAI viruses H5N1 and H5N8 were detected in the imported aquatic (geese and ducks) and exotic (yellow golden pheasant) birds. The samples tested negative for low-pathogenic Avian Influenza Virus (H9N2) as well as other avian viruses, viz., Avian avulavirus-1 (Newcastle disease Virus) and infectious bronchitis virus. This highlights the role of these resident and imported exotic birds in the local transmission and spread of the HPAI virus to domestic poultry. The findings call for proper biosecurity and quarantine measures for exotic and wild birds to reduce the potential risk to animal and public health in Nigeria.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.01.22.634354v1

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#UK - High pathogenicity avian #influenza #H5N1 viruses (#poultry) (Inf. with) - Immediate notification, 3rd

A 1.4 million egg laying and rearing flock. Increased mortality and other clinical signs were reported. Samples taken tested positive for HPAI H5N1. England, Shropshire Region.

Source: WOAH, https://wahis.woah.org/#/in-review/6209

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#UK - High pathogenicity avian #influenza #H5N1 viruses (#poultry) (Inf. with) - Immediate notification, 2nd

A 13,316 commercial turkey fattening unit. Increased mortality and other clinical signs were reported. Samples taken and tested positive for HPAI H5N1. England, East Riding of Yorkshire Region.

Source: WOAH, https://wahis.woah.org/#/in-review/6206

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#UK - High pathogenicity avian #influenza #H5N1 viruses (#poultry) (Inf. with) - Immediate notification

A 240 free-range layer unit. Increased mortality and other clinical signs were reported. Samples taken and tested positive for HPAI H5N1. England, East Sussex Region.

Source: WOAH, https://wahis.woah.org/#/in-review/6207

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Chronic Systemic #SARS-CoV-2 #Infection Without Respiratory Involvement in an Immunocompromised Patient

Abstract

In a patient on immunosuppressant treatment, SARS-CoV-2 RNA was documented in different extra-respiratory samples over several months in the absence of positive determinations in upper respiratory samples. Whole-genome sequencing of these samples showed the acquisition of different single-nucleotide polymorphisms over time, suggesting viral evolution and thus viral viability.

Source: Viruses, https://www.mdpi.com/1999-4915/17/2/147

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Association of #poultry #vaccination with interspecies #transmission and molecular #evolution of #H5 subtype avian #influenza virus

Abstract

The effectiveness of poultry vaccination in preventing the transmission of highly pathogenic avian influenza viruses (AIVs) has been debated, and its impact on wild birds remains uncertain. Here, we reconstruct the movements of H5 subtype AIV lineages among vaccinated poultry, unvaccinated poultry, and wild birds, worldwide, from 1996 to 2023. We find that there is a time lag in viral transmission among different host populations and that movements from wild birds to unvaccinated poultry were more frequent than those from wild birds to vaccinated poultry. Furthermore, our findings suggest that the HA (hemagglutinin) gene of the AIV lineage that circulated predominately in Chinese poultry experienced greater nonsynonymous divergence and adaptive fixation than other lineages. Our results indicate that the epidemiological, ecological, and evolutionary consequences of widespread AIV vaccination in poultry may be linked in complex ways and that much work is needed to better understand how such interventions may affect AIV transmission to, within, and from wild birds.

Source: Science Advances, https://www.science.org/doi/10.1126/sciadv.ado9140

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#USA, #H5N1 #birdflu is getting worse, but #Trump has silenced the #CDC

{Excerpts}

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The U.S. Department of Health and Human Services (HHS) has issued a gag order to the CDC, FDA and other departments by its acting secretary, informing them to terminate external communications before February 1, except for serious situations related to health and safety.

What do the FDA and CDC usually say? Nothing much, nothing that affects people's livelihood. They just send out a press release to tell everyone that a new drug has been approved, or issue new regulations, such as the previous rule that prohibits the use of red dye No. 3 in food. If it hadn't been released before Trump took office, it would not be released now.

There is even less content worth reading about the CDC, which only talks about the latest epidemics and how to deal with them, which are obviously not important. How can it be more important than the virtual currency issued by Trump's family?

HHS is the Department of Health and Human Services, and releasing information to the public is clearly neither healthy nor in the service of the public.

But here I have to defend Trump a little. When the US government is changing hands, it is not uncommon for the new government to ask all departments to temporarily stop external communications, mainly to ensure a smooth handover and avoid communication errors. However, this time is generally short, and the banned content is strictly limited, not a complete ban.

For presidents like Trump to impose a two-week ban on all visitors, it shows that previous presidents were not very smart. No one would have thought that they could do this.

Of course, now that the United States has the return of the wise and powerful President Trump, the situation is not just good, it is very good. No, it is not even very good, it is extremely good. Under such a gratifying situation, the CDC and other infectious disease control departments really have nothing to inform everyone.

For example, the CDC has a publication called Morbidity and Mortality Weekly Report. This is the worst kind of shit. It is updated every week and tells you how many people have died from this disease or what virus has been found. AIDS was first recorded in the Morbidity and Mortality Weekly Report.

Once the gag order is issued, the Morbidity and Mortality Weekly Report should also be suspended for at least two issues. I don't think there will be anything important in these two issues. It's just that the H5N1 highly pathogenic avian influenza is getting worse in the United States.

Originally, there should have been important updates in this regard in the Morbidity and Mortality Weekly Report in the next two weeks, but such trivial matters and a few broken viruses cannot cause any trouble. With Trump around, he is like a god protecting him.

Although the FDA just announced last Friday that it would inspect pet food safety because cat food was contaminated with H5N1 and more than a dozen pet cats across the United States became seriously ill or died, under Trump's command, the WHO was kicked out and the CDC was banned. I believe H5N1 will soon realize how powerful the United States is.

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Source: NetEase, https://m.163.com/dy/article/JMIUM39E0552CSHY.html

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Integrating #macroeconomic and public #health impacts in #social planning #policies for #pandemic response

Abstract

Infectious disease outbreaks with pandemic potential present challenges for mitigation and control. Policymakers make decisions to reduce disease-associated morbidity and mortality while also minimizing socioeconomic costs of control. Despite ongoing efforts and widespread recognition of the challenge, there remains a paucity of decision tool frameworks that integrate epidemic and macroeconomic dynamics. Here, we propose and analyze an econo-epidemic model to identify robust planning policies to limit epidemic impacts while maintaining economic activity. The model couples epidemic dynamics, behavioral change, economic activity, and feasible policy plans informed by respiratory disease threats of pandemic concern. We compare alternative fixed, dynamic open-loop optimal control, and feedback control policies via a welfare loss framework. We find that open loop policies that adjust employment dynamically while maintaining a flat epidemic curve in advance of the uncertain arrival of population-scale vaccination outperform fixed employment reduction policies. However, open loop policies are highly sensitive to misestimation of parameters associated with intrinsic disease strength and feedback between economic activity and transmission, leading to potentially significant increases in welfare loss. In contrast, feedback control policies guided by open loop dynamical targets of the time-varying reproduction number perform near-optimally when parameters are well-estimated, while significantly outperforming open loop policies whenever disease features and population-scale behavioral response are misestimated -- as they inevitably are. These findings present a template for integrating principled economic models with epidemic scenarios to identify vulnerabilities in policy responses and expand policy options in preparation for future pandemics.

Source: MedRxIV, https://www.medrxiv.org/content/10.1101/2025.01.21.25320900v1

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Collection of Avian #Influenza-Impacted #Wildlife in #Delaware Expanded Through DNREC-USDA Wildlife Services Effort

 {Excerpt}

DOVER, Del. (Jan. 22, 2025) – The Delmarva Avian Influenza Joint Information Center announced today that the Delaware Department of Natural Resources and Environmental Control (DNREC) and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) Wildlife Services are collaborating to collect sick and deceased snow geese and other wild birds that may have succumbed to the outbreak of avian influenza currently spreading throughout the state. 

The expanded statewide collection effort to help track the bird flu is funded through DNREC and the Delaware Department of Agriculture (DDA).

Sick or dead wild animals found in Delaware during the avian influenza outbreak or at any time of year, are to be reported to the DNREC Wildlife Section. 

Reporting deceased or ill wildlife does not guarantee that DNREC and APHIS Wildlife Services will respond to every report, only that a DNREC or APHIS Wildlife Services representative will assess the report, and if additional information is needed, may make follow-up contact.

State authorities also reiterated that the public should not pick up or handle any sick birds. 

Dead birds should not be picked up unless disposable plastic gloves are worn to handle them. This guidance also applies to waterfowl hunters – as the DNREC Wildlife Section has been made aware of hunters examining their harvest then moving ducks or geese to a game bag or carrying strap without following recommended precautions for wild birds that might have contracted avian influenza.

-- Anyone encountering sick or dead wild birds on private or public property should report their findings immediately to State authorities.

-- Report sightings of sick or dead wild birds through the DNREC Division of Fish and Wildlife’s sick, injured or dead wildlife reporting form.

-- Notify DDA if you find sick or dead poultry on your farm at poultry.health@delaware.gov.

If a resident finds a dead wild bird on their property and wants to remove it themselves, they should wear proper personal protective equipment (PPE), including gloves, a mask, and safety glasses, to dispose of it. 

Double-bag each dead bird found, zip-tie the bag and put it in the trash bin for pickup and disposal at a Delaware Solid Waste Authority landfill. 

Residents are also advised to carefully remove and dispose of all PPE in the dedicated trash bags and always wash their hands afterward.

Additionally, waterfowl hunters are advised to follow more focused protocols from APHISOpen this document with ReadSpeaker docReader for handling and field dressing any wild fowl they harvest in Delaware during an avian influenza outbreak.

Avian influenza is a highly contagious airborne respiratory virus that spreads quickly among birds through nasal and eye secretions and manure. 

Snow geese, which are waterfowl, are known to migrate from the Arctic and form large flocks in Delaware each winter. 

Due to close contact with thousands of other snow geese while feeding and roosting, they can get sick and die. 

It is unknown when or where the snow geese may have acquired the virus given their highly migratory nature and association with other waterfowl and waterbirds throughout the Atlantic Flyway through which they travel into Delaware and more southern states.

While the H5N1 virus has infected a small number of people across the U.S., there is no documented transmission of the virus between people in this country. Though the continued testing of people in close contact with animals infected with HPAI indicates a low risk to the general public’s health, children and pets should be kept away from wild birds and bird droppings.

If anyone in contact with wild birds or poultry begins to experience flu-like symptoms, please contact the Delaware Division of Public Health Office of Infectious Disease Epidemiology at 888-295-5156 (after hours) or 302-744-4990 (business hours) for a referral to a DPH clinic to obtain a flu swab test. 

Flu-like symptoms include fever, cough, sore throat, congestion, body aches, fatigue, and sometimes diarrhea. If symptoms seem severe, including trouble breathing, chest pain or pressure, dizziness/confusion, severe muscle pain, seizure, severe weakness or unsteadiness, worsening of chronic medical conditions, or fever or cough that begin to improve and then worsen or return, please dial 911 or visit the emergency department. Let hospital staff and providers know if you have been exposed to poultry or wild birds.

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Source: Department of Health, https://news.delaware.gov/2025/01/22/collection-of-avian-influenza-impacted-wildlife-in-delaware-expanded-through-dnrec-usda-wildlife-services-effort/

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Lack of Competence of #US #Mosquito Species for Circulating #Oropouche Virus

Abstract

Given recent outbreaks of Oropouche virus in Latin America and >100 confirmed travel-associated cases in the United States, we evaluated the competence of US vectors, including Aedes albopictus, Culex quinquefasciatus, Culex pipiens, and Anopheles quadrimaculatus mosquitoes. Results with historic and recent isolates suggest transmission potential for those species is low.

Source: Emerging Infectious Diseases Journal, https://wwwnc.cdc.gov/eid/article/31/3/24-1886_article

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Phylogeographic Characterizations of Recent (2015–2023) #Senecavirus A Isolates from #Canada

Abstract

Senecavirus A (SVA) continues to cause vesicular lesions in swine in Canada and many regions worldwide. Since the vesicular lesions caused by SVA are similar to those caused by foot and mouth disease virus, swine vesicular disease virus and vesicular stomatitis virus, a foreign animal disease investigation must be initiated to rule out these diseases. SVA isolates from pigs displaying vesicular lesions in Canada from 2015 to 2023 were sequenced, and phylogeographic analysis was performed using the complete genome sequences. The results infer that SVA has spread between the United States and Canada several times. In addition, the results suggest that SVA spreads from different regions. SVA spread was inferred from Canada into Thailand, India and Mexico and inferred from the United States to Brazil, Columbia, Chile and China with ten separate introductions. Furthermore, recombination was observed in SVA genomes from Canada, the United States and China.

Source: Viruses, https://www.mdpi.com/1999-4915/17/2/141

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Geographical #distribution and evolutionary #dynamics of #H4Nx avian #influenza viruses

Abstract

H4Nx avian influenza viruses (AIVs) have been isolated from wild birds and poultry and can also cross the species barrier to infect mammals (pigs and muskrats). The widespread presence of these viruses in wild birds and poultry and their ability to be transmitted interspecies make them an undeniable hazard to the poultry farming industry. In the present study, we collected fecal and swab samples from wild birds and poultry in Guangdong Province from January 2019 to March 2024, and various subtypes of AIVs were isolated, including 19 strains of H4 subtype AIVs. Further analysis was conducted on the internal genes of the 19 strains. These strains clustered together with high homology to highly pathogenic avian influenza virus (HPAIV), suggesting that H4Nx AIV may be reassorted from HPAIV. Two H4N8 strains are phylogenetically related to the porcine H4N8 AIV. Molecular characterization revealed that all viruses in this study were less pathogenic but had potential mammalian-adapted mutations. The transmission dynamics of H4Nx AIVs revealed that Europe and Asia, especially the Netherlands and Bangladesh, may be the centers of transmission. This may be linked to the migration of wild birds. The high migration rates from Russia to the Netherlands and from Russia to Bangladesh may also play a role. Therefore, continuous and systematic monitoring of wild birds to clarify the spatial and temporal distribution and prevalence of influenza viruses in wild birds is significant for early warning of avian influenza outbreaks in poultry and for risk assessment for public health and safety.

Source: Frontiers in Microbiology, https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1505203/full

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Unique #duck rearing practice in irrigated #rice paddy #fields driving recurrent #H5N1 avian #influenza #outbreaks in two districts of #Kerala, #India

Abstract

Highly pathogenic avian influenza (HPAI) outbreaks have repeatedly occurred in two districts of Kerala state, India, over the last few years. The outbreaks in the wetland areas coincided with the arrival of migratory birds. At the time, the factors responsible for local transmission in ducks were not known. This study aimed to identify the socio-economic factors responsible for spatial variation in the occurrence of HPAI outbreaks in the two districts using Bayesian network modelling (BNM) and Stochastic Partial Differential Equation (SPDE) model. Further, information was collected on the duck rearing practices in rice paddy fields to identify the risk factors for local – spread of the outbreaks. We found that the SPDE model without covariates explained variation in occurrence of outbreaks. The number of rice paddy fields used by the duck farmers was identified as risk factor. We concluded based on BNM and SPDE that the infected migratory birds were the source of infection for the first few duck farms in the wetland areas and subsequent transmission was driven by shifting of ducks from one rice paddy field to other fields. There is a probability of persistent and recurrent infections in the ducks and possible spill over to humans. Hence, it is important to have surveillance in ducks to prevent recurrent outbreaks in the region.

Source: Epidemiology and Infection, https://www.cambridge.org/core/journals/epidemiology-and-infection/article/unique-duck-rearing-practice-in-irrigated-rice-paddy-fields-driving-recurrent-h5n1-avian-influenza-outbreaks-in-two-districts-of-kerala-india/79211CF9EE6C556609C0460AA7735F05

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#WHO comments on #USA #announcement of intent to withdraw

The World Health Organization regrets the announcement that the United States of America intends to withdraw from the Organization.

WHO plays a crucial role in protecting the health and security of the world’s people, including Americans, by addressing the root causes of disease, building stronger health systems, and detecting, preventing and responding to health emergencies, including disease outbreaks, often in dangerous places where others cannot go.

The United States was a founding member of WHO in 1948 and has participated in shaping and governing WHO’s work ever since, alongside 193 other Member States, including through its active participation in the World Health Assembly and Executive Board. 

For over seven decades, WHO and the USA have saved countless lives and protected Americans and all people from health threats. Together, we ended smallpox, and together we have brought polio to the brink of eradication. American institutions have contributed to and benefited from membership of WHO.

With the participation of the United States and other Member States, WHO has over the past 7 years implemented the largest set of reforms in its history, to transform our accountability, cost-effectiveness, and impact in countries. This work continues.

We hope the United States will reconsider and we look forward to engaging in constructive dialogue to maintain the partnership between the USA and WHO, for the benefit of the health and well-being of millions of people around the globe.

Source: World Health Organization, https://www.who.int/news/item/21-01-2025-who-comments-on-united-states--announcement-of-intent-to-withdraw

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#Israel - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

A wild Eurasian buzzard in HaDarom region. Ashqelon: The outbreak occurred in an ecological park where poultry as ducks, guinea fowls, peacocks and wild birds are free living.

Source: WOAH, https://wahis.woah.org/#/in-review/6200

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#Chapare haemorrhagic fever- the Plurinational State of #Bolivia

Situation at a glance

On 7 January 2025, the International Health Regulations National Focal Point for the Plurinational State of Bolivia notified WHO of a laboratory-confirmed case of Chapare virus infection in an adult male from La Paz Department. 

Chapare haemorrhagic fever is an acute viral illness caused by Chapare virus. 

The virus was first identified in 2003 in Bolivia and has been associated with five documented outbreaks to date, all occurring within the country. 

These outbreaks have primarily affected rural areas in the La Paz Department, with the most recent case. 

There is no significant risk of international spread of the disease, as person-to-person transmission of the Chapare virus is possible but remains rare in the general population. 

As of 13 January 2025, no secondary cases have been reported, and all contacts remain without symptoms. 

Public health measures, such as disinfection and rodent control, have been implemented.

Description of the situation

On 7 January 2025, the International Health Regulations (IHR) National Focal Point (NFP) for the Plurinational State of Bolivia notified the World Health Organization (WHO) of one laboratory-confirmed human infection with Chapare virus (CHAPV) from one of the municipalities of La Paz Department. The patient is an adult male farmer in the age group of 50-60 years.

The patient developed symptoms including fever, headache, muscle pain, joint pain, and bleeding gums on 19 December 2024 and sought medical attention on 24 December. 

On 30 December, he was transferred to the local Health Center of the municipality due to worsening symptoms, where he died the same day. 

Blood samples were collected on 30 December before his death and sent to the National Center of Tropical Diseases (CENETROP), which confirmed CHAPV detection through real-time polymerase chain reaction (RT-PCR specific for CHAPV) testing on 2 January 2025.

An epidemiological investigation revealed significant risk factors for zoonotic disease transmission, including severe rodent infestation in and around the patient’s home. 

Environmental conditions such as wooden and corrugated metal housing, dirt floors, and peri-domestic coconut plantings created a conducive environment for rodent activity. 

The patient’s occupation as a farmer likely involved exposure to rodent burrows, further increasing the risk of infection.

Blood samples were collected from two close contacts of the case, which were negative. 

As of 13 January 2025, no secondary cases have been reported, and all identified contacts remain asymptomatic. 

Public health measures, including disinfection and rodent control, have been implemented, and investigations are ongoing. This is the fifth documented outbreak of Chapare haemorrhagic fever (CHHF) in Bolivia and globally since the virus was first identified in 2003.

Epidemiology

CHHF is a rare zoonotic disease caused by the CHAPV, a group of viruses belonging to the Mammarenavirus genus of the Arenaviridae family. These viruses are primarily transmitted to humans through infected rodents that serve as their natural hosts. 

Human transmission of Mammarenaviruses occurs mainly by inhalation of fine aerosol particles contaminated with virus-infected rodent excreta, such as urine, feces, or saliva.  

Human-to-human transmission is uncommon but has been documented, particularly in healthcare settings where infection prevention and control (IPC) measures are inadequate. This mode of transmission occurs through contact with the blood or bodily fluids of infected individuals and can be amplified during aerosol-generating medical procedures.

The incubation period ranges from 4 to 21 days, after which individuals may develop symptoms including fever, headache, muscle aches, vomiting, diarrhea, and in severe cases, haemorrhagic manifestations. Due to the nonspecific nature of early symptoms, CHHF can be challenging to diagnose, often requiring laboratory confirmation through methods like real-time polymerase chain reaction.

Currently, there is no specific antiviral treatment for CHHF; management focuses on supportive care to alleviate symptoms and maintain vital organ function. 

Case fatality rates for CHAPV infections range from 15% to 30% in untreated patients, with rates as high as 67% reported during outbreaks. 

Preventive measures emphasize reducing human exposure to rodent populations and implementing stringent IPC practices in healthcare settings to mitigate the risk of transmission.

CHHF is currently known to only occur in Bolivia. In the last 20 years, four outbreaks have been documented in the country. The first was reported in 2003 in Chapare Province, Cochabamba Department, involving a single fatal case. In 2019, a second outbreak occurred in La Paz Department, resulting in nine cases, including four deaths (case fatality rate: 60%). This second outbreak was caused by a different CHAPV strain than the one identified in 2003. The third outbreak took place in 2021 in La Paz Department, with three confirmed cases (two fatal). The most recent outbreak occurred in 2024 with one laboratory-confirmed case, also within La Paz Department.

Public health response

The local and national health authorities implemented the following public health measures:

-- Epidemiological investigation: A field investigation was conducted, during which rodent feces were detected. These feces did not belong to the known transmitter (Rattus rattus). The rodent infestation rate was calculated and found to be 75%.

-- Disinfection and rodent control: Disinfection measures and rodent control activities, including the use of rodenticides, were carried out both inside and outside the house.

-- Community surveillance: Health personnel, in collaboration with the municipal vector control program, conducted follow-up with families residing in the neighboring area of the case, due to the presence of rodents in these locations.

-- Community participation: Community engagement activities were carried out on 3 and 4 January 2025. These activities were planned by municipal and departmental health personnel to enhance awareness and participation in response efforts.

WHO risk assessment

One of the main challenges in detecting and responding to CHHF and other South American haemorrhagic fevers due to Mammarenavirus is the difficulty of making an early differential diagnosis due to the non-specificity of the initial clinical presentation. 

CHHF and other South American haemorrhagic fevers due to Mammarenavirus (e.g., Argentinian haemorrhagic fever, Bolivian haemorrhagic fever, and Sabia virus disease) should be considered for any patient presenting with suggestive symptoms originating from areas where Mammarenaviruses are known to circulate. 

These diseases should also be part of the differential diagnosis along with other endemic diseases such as malaria, dengue, yellow fever, and bacterial infections. 

Environmental exposures, such as evidence of rodent activity in or around the home, contact with rodent excreta, or visiting or working in areas where rodents are prevalent, should be carefully considered as key epidemiological risk factors. 

Case ascertainment should involve asking about exposure to rodents or contact with patients suspected of having haemorrhagic fevers due to Mammarenavirus. For biosafety reasons, all samples from suspected cases in regions where CHHF has previously been reported should be managed as Mammarenavirus samples, even for differential diagnosis.

In Bolivia, the geographical at-risk area is limited to rural areas in the northern part of the La Paz department, particularly along a jungle corridor from Caranavi to Teoponte municipalities, passing through the town of Palos Blancos, where the reservoir is found. 

Currently, CHHF is reported only in Bolivia. 

There is no significant risk of international spread of the disease, as person-to-person transmission of the Chapare virus is possible but remains rare in the general population. Continued surveillance, public awareness, and adherence to infection prevention and control measures are critical to preventing further spread and mitigating future outbreaks.

WHO advice

WHO recommends remaining vigilant and raising awareness among healthcare workers to detect, diagnose, and manage cases of haemorrhagic fever while ensuring strict compliance with infection prevention and control measures. Surveillance should focus on detecting suspected cases of haemorrhagic fever based on the clinical manifestations, travel history, and exposure history, tailored to the epidemiological context of the country or territory. Any individual who has had contact with the blood or bodily fluids of a suspected, probable, or confirmed haemorrhagic fever case during their illness is considered a contact. Contact monitoring should be performed for a maximum incubation period of 21 days following the last known exposure.

Laboratory confirmation of Mammarenavirus infection can be performed using various methods, including virological and serological techniques. However, the dynamics of Mammarenavirus infections (e.g., the duration of viraemia versus the appearance of antibodies) are not yet fully understood, and no serological assays have yet been validated for CHAPV. All biological samples should be treated as potentially infectious, handled only by trained personnel, and processed in suitably equipped laboratories.

Patients with suspected or confirmed CHHF should be isolated in a single room with a dedicated sink and toilet. Movement of patients with suspected or confirmed CHHF should be limited, however if patient ambulation outside of the room is necessary the patient should wear a medical mask during ambulation. All health and care workers in close contact with a patient with suspected or confirmed CHHF or who enter the isolation room should apply contact and droplet precautions, including the use of the following personal protective equipment: gown, examination gloves, medical mask, and eye protection (goggles or face shield). 

If an aerosol-generating procedure is performed on a patient with suspected or confirmed CHHF, the procedure should take place in a negative pressure airborne infection isolation room with the door closed. All health and care workers present in a room where an aerosol generating procedure is taking place should use airborne precautions in addition to contact and droplet precautions, including use of a fit-tested filtering facepiece respirator (e.g. N95). 

Routine cleaning and disinfection of the isolation room of a patient with suspected or confirmed CHHF should occur three times daily, and spot cleaning should occur immediately whenever there is a spill or material contamination of blood or body fluids. 

Cleaning may be performed with soap and water applied by cloth, followed by disinfection with a 0.5% sodium hypochlorite solution; allowing the disinfectant to remain wet and untouched on the surface for a contact time of at least five minutes. All disposable waste that is generated in the patient room should be managed as infectious waste. Linens from isolation rooms are advised to be bagged and handled using contact precautions during transport to laundry areas and washed separately from other patient linens. 

Reusable medical equipment used on a patient with suspected or confirmed CHHF should be labelled as biohazardous and managed appropriately during transport and reprocessing in a medical device reprocessing department. Patients should be advised to place the lid down when flushing their dedicated toilet to avoid generating bioaerosols.

Ribavirin has been described as a treatment option for haemorrhagic fevers caused by some Mammarenaviruses; however, its efficacy and safety have not been demonstrated in randomized clinical trials. Supportive care, including hydration, rest, and treatment of complications, is recommended. Evaluation and management of co-infections such as malaria, dengue, yellow fever, or bacterial infections should also be considered.

Further information

1) Control of Communicable Diseases. 21thEdition. Dr. David Heymann, Editor. 2022. American Public Health Association. Pag.44-47 

2) Toledo J., Paredes TorrezA., Alvaro Terrazas, Molina GutiérrezJ., Medina Ramírez A., Romero C., CondoriD., Alarcon de la Vega G., Swanson KortepeterM., Aldighieri S. Public health implications of a new world arenavirusoutbreak that occurred in Bolivia, 2019. Travel Medicine and InfectiousDisease. Vol 43, September - October 2021. Available: https://doi.org/10.1016/j.tmaid.2021.102124

3) Pan American Health Organization/World Health Organization. Epidemiological Alert: Haemorrhagic fever due to Arenavirus in Bolivia. 18 July 2019. Washington, D.C. PAHO / WHO. 2019.Available from:  https://www.paho.org/en/documents/epidemiological-alert-hemorrhagic-fever-due-arenavirus-bolivia-18-july-2019

3) US Centers for Disease Control and Prevention(US CDC). About Chapare Haemorrhagic Fever. Available from: https://www.cdc.gov/chapare/about/index.html

4) Loayza Mafayle R.,Morales-Betoulle ME., et al. (2022) Chapare Hemorrhagic Fever and Virus Detection in Rodents in Bolivia in 2019.  The New England Journal of Medicine 386;24:2283-2294. Available from: https://www.nejm.org/doi/full/10.1056/NEJMoa2110339

5) Plurinational State of Bolivia International Health Regulations National Focal Point.Email communication dated 7 January 2025. La Paz.; 2024. Unpublished.

6) World Health Organization. Clinical management of patients with viral haemorrhagic fever: A pocket guide forfront-line health workers. Available from:  https://www.who.int/publications/i/item/9789241549608

7) World Health Organization Laboratory diagnosis of New World Arenavirus infection. Available in Spanish from: https://www.paho.org/es/documentos/diagnostico-por-laboratorio-infeccion-por-arenavirus-nuevo-mundo

8) World Health Organization. Laboratory Systems. Available from:  https://www.paho.org/en/topics/laboratory-systems

9) World Health Organization. Transmission-based precautions (aide memoire). Available from: https://iris.who.int/handle/10665/356853

Citable reference: World Health Organization (20 January 2025). Disease Outbreak News; Chapare haemorrhagic fever in the Plurinational State of Bolivia. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON553

Source: World Health Organization, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON553

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