‘Wise to assume bird flu pandemic will cause more severe disease in humans than COVID-19’

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H5N1, or bird flu, has been perceived as a potential public health threat for at least 20 years now, since the virus infected some 18 people in China. Much recently, in 2022, the United States recorded its first human infection of avian influenza. Then, this April, a man in the US state of Texas contracted the disease from cows, creating an alarm in the global health community. 

Although the virus mainly spreads among birds, its pan-zootic profile is not unknown. But with every transmission to humans from a mammalian species, it becomes certain that H5N1 is growing more adaptive and the possibility of a human-to-human transmission becomes stronger, according to experts. 

There have also been speculation that bird flu can snowball into a pandemic. Its high virulence and fatality rate were highlighted in a news story published in the Daily Mail days after the Texas case. The story quoted Suresh Kuchipudi, a bird flu scientist in Pittsburgh, as saying: “Now, we are getting dangerously close to this virus potentially causing a pandemic”. He higlighted that the world needs to be prepared for such a global health challenge. 

Down To Earth spoke to Kudhipudi to understand the tendencies of the virus and the threats that it poses.

Himanshu Nitnaware: H5N1 has started assuming a deadly hue, particularly after we have just emerged from a global pandemic. Will you elaborate on this bird flu virus?

 

Suresh Kuchipudi: Bird flu viruses belonging to the H5N1 strain have been present for a long time. The original H5N1 virus was first identified in 1996 in a goose in China. These viruses later spread globally and underwent significant genetic changes and generated multiple subtypes.

The current bird flu virus subtype is known as H5N1 virus clade 2.3.4.4b, which initially emerged in Europe in the late 2020 and spread to many countries, causing significant outbreaks across multiple continents. Mass mortality events involving 2.3.4.4b clade viruses have been observed in several avian and mammalian species, including minks and sea mammals. The more recent development in this virus journey is the infection of cattle in the United States and a confirmed cow-to-human infection.

HN: It is not that a new virus has been circulating. Why should we be worried about it now? 

SK: The current subtype of the bird flu virus has shown an alarming ability to infect a wider array of wild birds and mammals. As it circulates among multiple hosts, there is a higher likelihood of genetic mutations, increasing the risk of viral evolution and potential adaptation to mammals.

HN: Since 2022, we have witnessed a few human infections. But is the number that high to be worried about? Or, in the evolutionary cycle of a virus, this breach is already worrying? 

SK: Human infections with H5N1 viruses have been documented over time, so the recent case of a Texas man infected with H5N1 isn’t entirely novel. However, what’s concerning is the unprecedented transmission among cattle before infecting a human. This situation presents multiple opportunities for the virus to infect diverse mammalian hosts, heightening the likelihood of adaptation.

HN: Bird flu is already on the scale of a pandemic. Do you see a particularly increasing infection and circulation of bird flu viruses in recent times? Does this imply that the next pandemic to hit humans will be from this source?

SK: The global distribution of H5N1 viruses primarily affects poultry, making them panzootic among birds. However, the concern arises from their potential to transition into a human virus, potentially triggering a human pandemic.

HN: If it causes the next pandemic, will it be a severe one, comparable to the COVID-19 one?

SK: While we cannot accurately predict the severity of the virus after gaining human-to-human transmission capability, it’s prudent to assume, for preparedness in a global health emergency, that it’s likely to cause more severe disease in humans than COVID-19, based on current information.

HN: The virus cannot survive on a dead body, it requires the host to be alive for its existence. If it does become deadly, how can infection-spread behaviour be known? 

SK: SARS-CoV-2, the cause of the COVID-19 pandemic, primarily spread among humans globally. The potential occurrence of a H5N1 bird flu pandemic could introduce complexity in virus circulation involving both humans and other animal hosts. This scenario could pose significant challenges for mitigation and control efforts.