Bird flu is back: how worried should we be?

As a disease detective, the danger of the next pandemic is always on our radar. The 1918 flu pandemic, which killed 50 to 100 million people and infected one-third of the population of just 1.5 billion, showed how deadly a flu pandemic could be. There are four types of influenza viruses: A, B, C, and D. Of them, A and B are the causes of flu season every year. Influenza A is considered the only influenza virus to have the potential to cause a major pandemic in humans.

For the above reasons, the world was concerned about the next flu pandemic and WHO has set up alert systems around the globe since 1952 to identify any new changes in the influenza virus, which could increase its capacity to infect others or become more lethal.

In 2007, a poultry farm in Abbottabad got infected with bird flu (H5N1). As a standard procedure, the stock was culled to prevent infection spreading to other farms. The person who was responsible for culling developed flu-like symptoms and got some medical aid. After a few days, when his situation did not improve, he moved to Peshawar and went to a local hospital. As his situation worsened, he was admitted to the hospital and later shifted to the ICU. While he was being treated, a few of his brothers developed the same symptoms, and two of them later died one after another while the original patient recovered. As some other related people, including a physician, started to report similar symptoms the treating consultant sent the samples on the suspicion of H5N1. Until then, there was no known human case of H5N1 in Pakistan, and it was a rare human disease anyway. By the time the final diagnosis came, and the world knew about the threat of another potential human flu pandemic, it was already close to 40 days from the start of culling.

I had just started my work as a US-CDC Resident Adviser for the Pakistan Field Epidemiology and Laboratory Training program (FELTP), and we had to quickly develop a training module to train both veterinarians and medical doctors to manage and control a potential pandemic. I also have to send some of my students to help the provincial government investigate the outbreak. But within four days, I received an email from Washington, DC, saying that a Pakistani has been admitted to a hospital in New York with flu-like symptoms, and he is giving the history that two of his brothers have died of bird flu, and he was back in Pakistan for their burials. It really sent shockwaves of failures in detect and control systems and also showed that it is actually impossible in today’s world to stop any infectious diseases at the borders. Luckily, he had the simple flu, and H5N1 human-to-human transmission was limited and not sustained.

The current bird flu strain is infecting mostly poultry, and hundreds of millions of birds across the globe have been culled. That is why global prices of poultry and eggs went up in many western countries. However, it has also spilled from poultry to different animals, most recently cows. Last week in the US, the second case of human bird flu was identified in a person who probably got it from cows. He has mild symptoms.

In Pakistan, there has been no case of H5N1 in poultry reported for more than a decade. However, India reported it in its poultry in 15 states and its first human case and death in 2021. Pakistan follows the policy of carpet vaccination among its commercial poultry, but the US and Europe have a different policy of not vaccinating poultry to avoid the emergence of resistant strains and instead culling birds to stop the transmission.

The world is cautious but not in panic, as the human-to-human transmission of H5N1 until now has not been sustained for very long. However, the recent pandemic of SARS-CoV-2 (Covid-19) has also shown that any virus could change itself to become lethal and more infectious and cause a major epidemic or pandemic. We need to have a good-quality global health intelligence system to safeguard our populations.

Published in The Express Tribune, April 9^th, 2024.

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