{Excerpt} Time Period: March 16 - March 22, 2025 -- H5 Detection : 5 sites ( 1.2% ) -- No Detection : 401 sites ( 98.8% ) -- No samples in last week : 211 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html ____
{Excerpt} Time Period: March 09 - March 15, 2025 -- H5 Detection : 12 sites ( 2.7% ) -- No Detection : 431 sites ( 97.3% ) -- No samples in last week : 177 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html ____
{Excerpts} Recent updates Laboratory CDC completed serology testing on blood specimens from close contacts of a child with mild illness in San Francisco who was confirmed to be positive for avian influenza A(H5N1) virus, though, there were no known animal exposures associated with that case. -- Serology testing was conducted to look for antibodies to influenza A(H5N1) virus in this child, which would indicate recent infection. -- The child's blood was tested and found to have antibodies to avian influenza A(H5N1) virus. -- None of the close contacts of the case in San Francisco who were tested had antibodies to avian influenza A(H5N1) virus, which supports the conclusion that none of these close contacts were infected , and that no person-to-person spread occurred among these close contacts. -- These findings are reassuring. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States. CDC has sequenced the virus from...
Time Period: March 02 - March 08, 2025 - H5 Detection : 29 sites ( 6.2% ) - No Detection : 438 sites ( 93.8% ) - No samples in last week : 152 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html ____
Summary -- What is already known about this topic? - Persons with occupational exposure to highly pathogenic avian influenza (HPAI) A(H5N1) virus–infected dairy cattle are at increased risk for infection. -- What is added by this report? - During September 30–December 24, 2024, a total of 38 persons received a positive test result for HPAI A(H5N1) viruses in California ; 37 were dairy farm workers with occupational exposure to sick cows. One, a person aged <18 years with an undetermined exposure , was the first pediatric patient detected with influenza A(H5) infection in the United States. -- What are the implications for public health practice? - Public health agencies should investigate influenza-like illness or conjunctivitis in workers with occupational exposure to animals infected with HPAI A(H5N1) virus. Thorough investigations of all human HPAI A(H5N1) virus infections are necessary to identify potential exposure sources, including monitoring the virus for co...
{Excerpt} Time Period: February 23 - March 01, 2025 - H5 Detection : 8 sites ( 1.8% ) - No Detection : 445 sites ( 98.2% ) - No samples in last week : 100 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html ____
As of February 28, 2025 CDC assessed the risk from H5N1 viruses to the U.S. general population and to populations in the United States with contact with potentially infected animals, including through contaminated surfaces or fluids . Risk describes the potential public health implications and significance of an outbreak for populations assessed. See definitions below for more detail. {Risk posed by H5N1 viruses to the United States. Please see methods section for further information on definitions of terms.} ___ The purpose of this assessment is to evaluate the current public health risk of H5N1 viruses to the general U.S. population and to those in contact with potentially infected animals or contaminated surfaces or fluids, and to inform public health preparedness efforts. CDC assessed risk by considering both likelihood and impact of infection in each population (...). Both the likelihood and impact of infection are assessed at a population level. Likelihood of infection refers to ...
{Excerpt} Time Period: February 16 - February 22, 2025 -- H5 Detection : 10 sites ( 2.6% ) -- No Detection : 379 sites ( 97.4% ) -- No samples in last week : 75 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html ____
Summary -- What is already known about this topic? - Highly pathogenic avian influenza A(H5N1) outbreaks have emerged in U.S. cattle and poultry . Wastewater surveillance detects influenza A(H5) subtype but does not currently distinguish between human and animal sources. -- What is added by this report? - During September 15, 2021–July 11, 2024 , retrospective analysis of wastewater surveillance data revealed 21 avian influenza A(H5) subtype detections across 12 Oregon communities . No association was found between detections in a community’s wastewater and history of a poultry outbreak or presence of dairy processing facilities or dairy farms within the sewershed. Avian influenza A(H5) was detected most frequently in two communities with important wild bird habitats . -- What are the implications for public health practice? - Wastewater surveillance was an early indicator of avian influenza emergence in Oregon. Nonhuman and noncattle animal inputs , including wild bir...
{Excerpts} (...) Epidemiology Updates As of February 24, CDC has confirmed three human cases of H5 bird flu in people who became ill in 2025: -- a dairy worker with exposure to infected dairy cows (Nevada), -- a poultry worker with exposure to infected commercial poultry ( Ohio ), and -- the owner of an infected backyard poultry flock ( Wyoming ). These are all considered higher-risk exposures . While the dairy worker was not hospitalized , both people with poultry exposures experienced severe illness and were hospitalized . Both hospitalized cases were confirmed positive from lower respiratory specimens , including a bronchoalveolar lavage and sputum . To date, there has been no evidence of onward spread from any of these people to anyone else . The dairy worker in Nevada had conjunctivitis (eye redness and irritation) and has recovered . Most infections associated with U.S. dairy cows to date have involved mild respiratory symptoms or conjunctivitis. This perso...
{Excerpt} (...) Time Period: February 09 - February 15, 2025 -- H5 Detection : 12 sites ( 3.3% ) -- No Detection : 348 sites ( 96.7% ) -- No samples in last week : 94 sites Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html _____
Summary -- What is already known about this topic? - Outdoor cats on U.S. dairy farms have been infected with highly pathogenic avian influenza (HPAI) A(H5N1) virus; infection has not been reported in indoor cats. -- What is added by this report? - HPAI A(H5N1) virus was detected in two indoor domestic cats with respiratory and neurologic illness that lived in homes of dairy workers but had no known direct exposure to HPAI A(H5N1)–affected farms. Both dairy workers declined testing ; other household members received negative test results for influenza A. -- What are the implications for public health practice? - Veterinarians in states with confirmed HPAI A(H5N1) in livestock should consider obtaining household occupational information , testing for influenza A viruses , and wearing personal protective equipment when evaluating companion cats with respiratory or neurologic illness . Suspected cases should be reported to public and animal health officials. Abstract High...
{Excerpt} Time Period: February 02 - February 08, 2025 -- H5 Detection : 15 sites ( 3.9% ) -- No Detection : 372 sites ( 96.1% ) -- No samples in last week : 63 sites (...) Source: US Centers for Disease Control and Prevention, https://www.cdc.gov/bird-flu/h5-monitoring/index.html _____