The COVID-19 pandemic has killed over 1.2 million Americans and over 7 million worldwide. The 1918 Spanish Flu pandemic killed an estimated 675,000 Americans and 40 to 60 million globally. It’s not a question of if we will have another pandemic, but when. Will it be a virus yet unknown or a new stain of COVID or influenza? No one knows.
Avian influenza (bird flu) has the potential of becoming a pandemic virus. Periodically it proliferates in wild migratory birds. Currently, a highly pathogenic avian influenza A(H5N1) is pandemic in bird populations.
Concern increases when bird flu infects domesticated poultry populations like chickens, turkeys, and ducks. When the virus mutates and jumps to pigs or cows, apprehension rises since the virus has adapted to mammals. With further mutations, the virus could infect another mammal – humans.
Rarely, individual human infection occurs with prolonged close contact with infected poultry or other animals. That’s where the transmission almost always ends. The virus is not “human-like” enough to support further human transmission.
Pigs are especially adept at being infected by various animal flu types. Suppose a pig is infected with a bird and human flu virus simultaneously; the two viruses could mix their genomes when replicating to produce a new more human-like virus supporting unsustained human-to-human spread. Alternatively, a human could be infected simultaneously with a bird and human virus giving a similar result.
With progressive mutations, the virus could advance to sustained human-to-human spread. Human clusters of infection without close animal exposures signal a terrifying situation. People would have little or no preexisting immune protection to this novel virus. The 1918 Spanish flu included avian components.
According to the U.S. Department of Agriculture, A(H5N1) is widely infecting poultry and has jumped to dairy cattle, largely asymptomatically. The first herd infected from migratory birds was in December 2023 in Texas. Now, at least 151 U.S. herds of dairy cattle (the virus adapted to bovine mammary glands) in 13 states are infected, and infections could potentially spread worldwide. The Centers for Disease Control and Prevention reports the virus has infected eight individuals in the U.S. with prolonged close exposure to dairy cattle or farm poultry.
The virus is widespread in milk and other dairy products. The Federal Food and Drug Administration reports no viable virus found in pasteurized milk and deems the pasteurized milk supply as safe. However, unpasteurized milk is legal for sale in 30 states.
The eight human cases are probably just the tip of the iceberg. Although the risk to humans remains low, we were caught unprepared for COVID-19, and vigilance is warranted for avian flu.
There should be intensified surveillance and testing of poultry, dairy cattle, and pigs. The USDA requires testing of dairy cattle transported over state lines, but testing is voluntary on the state level. That’s a problem. Herd isolation and quarantine measures should be implemented.
Continued testing of the milk supply, wastewater, and especially at-risk individuals is important. We need to further vaccine development and offer vaccination to frontline farm-related workers if things progress.
Local health departments must have standardized protocols and financial support for adequate infrastructure to address an avian flu pandemic. Farmers must receive informational resources about bird flu and be financially supported for preventative and unforeseen costs. Warnings should be issued regarding unpasteurized milk-product consumption.
Influenza is an unpredictable virus; monitoring for worrisome genetic changes is essential.
If a pandemic occurs, let’s not let this one get away from us.
Richard D. Feldman, M.D. is an Indianapolis family physician and former Indiana State Health Commissioner who served in the administration of Governor Frank O’Bannon.