Explainer-Bird flu: what are the risks to people and animals?

[February 15, 2023]  By Tom Polansek

(Reuters) - Countries ranging from the United States and Britain to France and Japan have suffered record losses of poultry in outbreaks of avian flu in the past year.

The disease, which experts said is being spread by migratory birds, reached South American nations such as Ecuador, Peru and Bolivia for the first time.

SHOULD HUMANS WORRY ABOUT INFECTIONS?

The risk to humans is low, said Tedros Adhanom Ghebreyesus, director-general of the World Health Organization. As a precaution, people are advised not to touch dead or sick wild animals.

Globally, 868 human infections with H5N1 avian flu - the type of virus circulating around the globe - were reported from 21 countries from January 2003 to Nov. 25, 2022, according to the WHO. Of these cases, 457 were fatal, about 53%.

In January, the WHO reported the first known human case of the avian flu H5 virus in Latin America and the Caribbean - an infection in a nine-year-old girl in rural Ecuador. The girl, who was in contact with backyard poultry, was hospitalized, the agency said on Jan. 18.

Human cases are usually the result of direct or indirect exposure to infected live or dead poultry or contaminated environments, the WHO said.

WHICH COUNTRIES HAVE BIRD FLU?

At least 60 countries have killed poultry in response to bird flu outbreaks since October 2021, according to data the Paris-based World Organisation for Animal Health provided to Reuters. Among the countries affected are India, Taiwan, Nepal, Peru, the Czech Republic, Romania, and Niger, the intergovernmental group has said.

WHAT BIRDS CAN BE INFECTED?

Wild birds including waterfowl like ducks can carry bird flu viruses without appearing sick and easily spread them to domesticated poultry like chickens and turkeys, experts said.

CAN OTHER SPECIES BE INFECTED?

Mammals including bears, seals, foxes and skunks have been infected with H5N1 avian flu, authorities said.

A person holds a test tube labelled "Bird Flu", in this picture illustration, January 14, 2023. REUTERS/Dado Ruvic/Illustration

WHAT HAPPENS TO POULTRY THAT BECOME INFECTED?

Highly pathogenic avian flu, such as the type that is circulating globally, can cause disease that affects multiple internal organs, with mortality up to 90% to 100% in chickens, often within 48 hours, according to the U.S. Centers for Disease Control and Prevention.

If one bird in a flock has avian flu, farmers usually cull all their birds to prevent the spread of the highly contagious virus.

HOW DOES THIS AFFECT FOOD SAFETY?

As part of government response plans, infected birds are excluded from the food supply. Additionally, avian flu is not transmissible by eating properly cooked poultry and eggs, the U.S. Department of Agriculture said.

HOW DID THE OUTBREAK GET SO BAD?

The ongoing global outbreak of H5N1 avian flu traces back to the first detection of the goose guangdong lineage of the H5 virus in Hong Kong in 1996, disease experts said.

Dabbling ducks in Asia adapted over time so they could carry the virus without dying, said John Clifford, a former chief veterinarian for the U.S. Department of Agriculture. The virus then made its way into breeding grounds and through migratory pathways around the world, said Clifford, now the veterinary trade policy advisor for the USA Poultry and Egg Export Council, an industry group.

(Reporting by Tom Polansek. Additional reporting by Sybille de La Hamaide in Paris; editing by Caroline Stauffer and Claudia Parsons)

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