Wednesday, February 21, 2024

Risk of AI infection in humans regarded as low

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By Barbara Olejnik

Poultry Times Staff

bolejnik@poultrytimes.com

GAINESVILLE, Ga. — While the U.S. has recently experienced great losses in the poultry industry as a result of outbreaks of avian influenza — a total of 48 million birds have been killed — there has not been any human infection.

The Centers for Disease Control and Protection regards the risk to humans of infection from avian influenza in poultry flocks to be low.

However the agency is advising people to stay away from sick or dying birds. If necessary the CDC advises wearing coveralls, face masks and eye protection.

“The best way to prevent infection with avian influenza A viruses is to avoid sources of exposure,” the CDC stated.

Work is underway on a possible vaccine targeted to avian influenza cases in humans, but is not yet available. Seasonal influenza vaccination will not prevent infection with avian influenza A viruses, but can reduce the risk of co-infection with human and avian influenza A viruses.

Avian influenza A virus infection in humans cannot be diagnosed by clinical signs and symptoms alone; laboratory testing is required. The CDC currently recommends oseltamivir, peramivir or zanamivir for treatment of human infection with avian influenza A viruses.

Although there have not been any AI outbreaks in the U.S. since mid-June, USDA officials are preparing for a possible return of the virus this fall when wild birds again begin their migrations to warmer climates.

Most avian influenza viruses do not cause disease in humans. However, some are zoonotic, meaning that they can infect humans and cause disease. The World Health Organization notes that most well-known example is the avian influenza subtype H5N1 viruses currently circulating in poultry in parts of Asia and northeast Africa.

Most human infections with avian influenza A viruses have occurred following direct or close contact with infected live or dead poultry. Disease in humans has ranged from mild to severe. There is no evidence that the disease can be spread to people through properly cooked food.

The A(H5N1) virus subtype first infected humans in  1997 during a poultry outbreak in Hong Kong SAR, China. Since its widespread re-emergence in 2003 and 2004, this avian virus has spread from Asia to Europe and Africa ad has become entrenched in poultry in some countries.

From 2003 through July 17, 2015, 844 laboratory confirmed human cases of avian influenza A (H5N1) virus infection have been officially reported to the World Health Organization from 16 countries. Of these cases, 449 have died.

Outbreaks of some AI viruses among poultry have been associated with illness and death in humans in Asia, Africa, Europe, the Pacific and the Near East. While very rare, avian influenza A viruses have also caused illness in humans in the U.S. However, the U.S. cases involved low path AI viruses.

In November 2003, a case of avian influenza A virus was detected in an adult male from New York who was hospitalized for respiratory tract illness from a low pathogenic avian influenza A (H7N2). The source of the infection is unknown.

In 2002, a person involved with culling activities developed influenza-like illness when low pathogenic avian influenza A(H7N2) outbreak occurred among turkeys and chickens at commercial farms in Virginia. No human-t-human transmission was evident and the person made a full recovery.

Up until the latest U.S. outbreaks of highly pathogenic avian influenza, which began in December 2014, the U.S. had not experienced any HPAI outbreaks in 20 years. In February 2004, an outbreak of HPAI (H5N2) virus was reported in a flock of 7,000 chickens in south-central Texas. No transmission of the virus to humans was reported.

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