International Events

Avian Influenza A(H5N1) USA 9 April 2023


  • On the first of April 2024, WHO has been notified of a laboratory-confirmed case of human infection with influenza A(H5N1) virus by the National IHR Focal Point (NFP) of the United States of America.
  • The patient developed symptoms on March 27 and had a history of exposure to dairy cows infected with influenza A(H5N1) virus in Texas. This confirmed human case of influenza A(H5N1) is the first to be detected in 2024 and the second in the country. No additional cases associated with human infection with influenza A(H5N1) have been identified.

Risk Assessment:

  • This human case was reported to have been exposed to dairy products in Texas, and HPAI A (H5N1) has been confirmed in dairy herds.
  • Most human cases occur after exposure to infected animals or a contaminated environment. Reported human infections tend to be mild clinical illnesses, and more human infections can be expected as the virus continues to be detected in poultry flocks and pig populations. However, influenza A infection in bovine species is rarely reported, and its spread among herds is currently being evaluated. Dairy cattle in four US states.
  • From 2003 to April 2024, a total of 889 cases and 463 deaths (52% mortality) due to influenza A(H5N1) virus have been reported worldwide from 23 countries. The last reported case in humans before the current case was in March 2024 in Vietnam. The human case in Texas is the fourth case reported in the Americas region, with the most recent previous case reported in Chile in March 2023.
  • Current epidemiological and virological evidence suggests that influenza A (H5), A (H9N2), A (H1) v, and A (H3N8) viruses have not acquired the ability for sustained human-to-human transmission, and therefore the likelihood of human-to-human transmission is low.
  • There are no specific vaccines to prevent influenza A(H5N1) virus infection in humans, but vaccine candidates have been developed to prevent H5 virus infection in humans for pandemic preparedness purposes.

WHO Recommendations for Risk Management:

  • The diversity of zoonotic influenza viruses requires increased surveillance in both animals and humans, in addition to comprehensive screening for each zoonotic infection, and epidemiological planning. To prevent a viral mutation that could make human-to-human transmission easier, the World Health Organization also recommends that poultry workers receive seasonal influenza vaccination.
  • Global surveillance to detect virological, epidemiological, and clinical changes associated with the spread of influenza viruses that may affect human and animal health. And cooperation between the animal and human health sectors. And follow up on suspected human cases systematically.
  • If traveling to countries with known outbreaks of animal influenza, you should avoid farms, contact with animals in live animal markets, entering areas where animals may be slaughtered, or touching any surface contaminated with animal waste. Travelers should also wash their hands frequently with soap and water. The community in general must also follow good food safety and hygiene practices.
  • All laboratory-confirmed human infections caused by a new influenza virus subtype must be reported under the International Health Regulations (International Health Regulations, 2005).
  • WHO does not recommend special screening of travelers at points of entry or restrictions regarding the status of influenza viruses at the human-animal interface.


Last Update : 29 April 2024 12:33 PM
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