Every Human Case of Avian Flu Reported So Far

Human cases remain rare but the risk of an outbreak could change at any time.

avian flu cases in humans

Analysis Health Public Health

Public health officials are urging governments to prepare for possible avian flu spillover to humans. The disease is now spreading between mammals including foxes, otters, sea lions and bears. And while human cases remain extremely rare and the risk to the human population is low, health officials warn the situation — and risk level — could change at any moment. On February 22, an 11 year old girl died from bird flu, according to Cambodian health authorities.

While evidence points to earlier outbreaks of avian influenza in humans — including the 1918 flu — the first recent case occurred in 1997. An outbreak in chickens in Hong Kong led to 18 human cases — six of which were ultimately fatal. More widespread outbreaks in 2003 led to new infections and since then — more than 860 human cases of the H5N1 strain have been diagnosed globally. 

Every Case of Bird Flu in Humans

According to the World Health Organization, there have been 244 documented human infections of H5N1 since 2003 in the Western Pacific region: Cambodia, China, Laos and Vietnam. Of the 244 cases, 136 were fatal — a mortality rate of 56 percent.

Other strains of avian flu have also been reported in humans over the years. Since 2014, 84 infections of H5N6 have led to 33 deaths. China has been the site of many human infections, including the country’s first case of H7N9 in 2013, leading to more than 1,500 cases and numerous deaths, according to the World Health Organization. China reported one case of H7N4 in 2018 and in November 2022, saw 85 cases of H9N2. Two were found in Cambodia.

In addition, three cases of H3N8, one of which resulted in a death, have been found in Western Pacific nations and two H10N3 cases have been detected globally.

‘Constant Vigilance and Ongoing Surveillance’

At this time, avian flu presents little danger of widespread infection in humans, but the level of risk may not remain the same, warned the World Health Organization on February 8. “[W]e must prepare for any change in the status quo,” said Dr. Tedros Adhanom Ghebreyesus, Director General of the WHO.

For now, the agency expects “sporadic human cases” — typically caused by direct contact with animals — and potentially “small clusters” of human infections.

The U.S. Centers for Disease Control and Prevention seems to agree, considering the highly virulent H5N1 strain “primarily an animal health issue.” Both agencies, though, are closely following the situation and recommend that governments around the world do the same. “[C]onstant vigilance and ongoing surveillance for novel influenza viruses worldwide is needed in people and animals — especially in poultry and pigs,” writes the CDC. 

Resurgence of Avian Flu

While the majority of the world’s identified cases have occurred in the Western Pacific region decades ago, sporadic cases have surfaced in recent years as farmed and wild bird populations experience unprecedented outbreaks.

In Laos, a one-year-old infant was hospitalized in October of 2020. Infected with H5N1, the young patient experienced fever and difficulty breathing, among other symptoms.

On January 6, 2022, the first human case of H5N1 in the U.K. was reported by England, found in an individual who was asymptomatic and considered to not be infectious. Marking another first, China confirmed its first case of H3N8 on April 27, 2022 — a four-year-old child with close contact to birds at home. 

Just one day later, on April 28, the U.S. confirmed its first human infection with H5N1, discovered in an individual who had been working in the culling of farmed birds exposed to avian flu. Until that time, there had been just 4 cases of avian flu reported by the U.S., all in the form of less pathogenic strain H7N2.

Highly pathogenic bird flu is thought to have first emerged in U.S. poultry in 1924, which “caused severe losses in live bird markets in New York City,” according to the Centers for Disease Control. While there has been no documented human-to-human spread of avian flu anywhere around the world, there is some debate as to the origins of the deadly 1918 flu pandemic that killed 20-40 million people globally. The CDC writes that the influenza responsible did have “genes of avian origin,” as did a 1957 pandemic that killed 1.1 million people worldwide.

The world’s most recent reported case of H5N1 occurred in China. A 38-year-old woman was hospitalized on September 22, 2022 and died not long after, on October 18.

Health Officials Are on Alert

There are multiple health threats facing the public this winter — from seasonal flu to RSV to a resurgence of norovirus. As a result, U.S. health officials say we cannot let our guards down and assume that avian flu will not become a bigger threat.

Health officials are keeping an eye out for signs that might change their risk assessment. The Centers for Disease Control is monitoring for multiple confirmed cases of avian flu spreading from birds to humans, for example, as well as the identified transmission of the virus from one infected human to another.

CDC officials recommend a number of preventative measures, like avoiding direct contact with birds, either wild or farmed. Another important precaution is to get your seasonal flu shot. While the current flu shot does not prevent against avian flu, agency officials say it can help reduce the risk of getting sick with seasonal and avian flu at the same time, which is an important risk reduction measure.

This piece has been updated at the top to clarify that the first human case of avian flu was not in 1997. Multiple sources suggest the 1918 flu, among others, were avian in origin. The 1918 and 1957 pandemics were already included but an earlier version used the wording “first case” in reference to the 1997 outbreak.

This piece has been updated to include a new fatality.

This piece has been updated to include the most recent data from the WHO.

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