Not just for the birds

Since March, bird flu, which in recent years yielded to Covid in the index of worldwide disease concerns, has been back in the news after outbreaks among dairy cows in multiple states and at least one infection in a farmworker in Texas. The influenza virus, called highly pathogenic H5N1, can be transmitted by wild birds to domestic poultry and other bird and animal species. Dr. Seung Kang, The Floating Hospital’s infectious disease specialist, said sporadic cases of infected mammals have been reported, but its spread among cows was unexpected. “Scientists are concerned that bird flu in cattle could become a permanent reservoir for the virus, giving it more chances to mutate and spread to humans.” Although the virus does not usually infect humans, sporadic human infections have occurred from close contact with infected animals. Dr. Kang said it is important to note that “highly pathogenic” refers to severe impact in birds, not necessarily in humans. The Centers for Disease Control stated on May 10 that the risk to humans is still considered low.

Not a new virus

Dr. Kang noted this strain of bird flu has been around for a considerable time. “In 1996, the first case was identified in a domestic waterfowl in China, and the next year, the virus caused large poultry outbreaks in Hong Kong, resulting in 18 human infections. The 1997 outbreak was contained, but the virus re-surfaced in 2003 and spread widely in birds throughout Asia, causing poultry outbreaks and sporadic human infections.” From that point, she said it has become established as an endemic virus in poultry and ducks in those regions. According to the CDC, the virus spread from wild birds to poultry in Europe in 2005, and after mutating a few times, it eventually made its way to North America in 2021, when it was detected in wild birds in the United States and Canada. In 2022, a person working with infected poultry in Colorado tested positive for the virus but had mild symptoms of fatigue and recovered. The farm worker in Texas also has recovered from mild eye irritation and redness. Since 2003, 880 people from 23 countries were reported to have contracted the virus, according to the World Health Organization. Of these cases, 463 were fatal — a high mortality rate. “Yes, it can become a threat to humans, but that is just a possibility,” Dr. Kang said. “there’s no evidence as of now that it can spread from human to human quickly.” What Dr. Kang said is concerning is the emergence of the virus here in livestock. Mammals are closer to humans in their biological makeup than birds. WHO noted last summer that some mammals could even “act as mixing vessels for influenza viruses, leading to the emergence of new viruses that could be more harmful to animals and humans.” Dairy workers are often in contact with the cows, increasing the possibility of an infection.

Prevention, medicine and monitoring

The virus has responded well so far to medications such as Tamiflu, Dr. Kang said. Since the strain has been around for a while, the CDC and other agencies in the United States and elsewhere have tracked H5N1 for years to monitor its evolution. She added, “We have antivirals, and capacity to ramp up the vaccine production.” The CDC already has two candidate viruses that can be used to make vaccines and the Biomedical Advanced Research and Development Authority has enough building blocks for vaccines to make millions of doses in weeks. Mass production could also ramp up quickly if needed. Earlier this month, she said government agencies like the United States Department of Agriculture, Food and Drug Administration and the CDC would need to increase their monitoring of people who have regular contact with livestock. At the time of this writing, 70 workers are being followed by the state of Colorado after exposure to the H5N1 virus at a dairy farm there. The FDA recently conducted PCR testing in 96 commercially purchased milk products and found genetic traces of the H5N1 virus in 1 in 5 samples, but Dr. Kang noted that the early data show no presence of live virus. She added, “Pasteurization kills the virus and leaves behind only inactive fragments that do not have the potential to infect humans.” The CDC has recommended avoiding milk that is not pasteurized, also known as “raw milk,” until the risk of infection from it is known. On May 10, the USDA announced it would offer dairy farmers financial incentives to test their cattle. The CDC is also monitoring and sharing data on flu indicators found in wastewater, looking for unusual spikes at a time when the flu isn’t typically active. Avoiding and addressing the risks Dr. Kang said workers with prolonged exposure to cattle who have symptoms such as fatigue, headache, fevers, respiratory issues or the eye irritation suffered by the patient in Texas, should be tested. However, exposure to infected birds also poses a risk, as in the earlier poultry farm case from Colorado. Any dead bird could be a potential carrier of the virus, she noted. Therefore, anyone encountering a dead bird or animal in a yard, park or the woods should avoid touching it. If there is contact with the hands, secretions and excretions could end up in the eyes or mouth where the virus could be introduced to the body and potentially cause infection. Infectious droplets can also be inhaled at close range, she added. Anyone who has developed symptoms from such exposure should be tested. “The virus doesn’t seem to have acquired the ability to infect humans efficiently yet,” she noted. While that is reassuring, she said the H1N1 epidemic, what we called “swine flu” in 2009, started with the report of a single case in March. By the next month, “we could see it everywhere in the world. That’s how fast it can spread once the virus gains the ability to infect humans.” Monitoring groups at high risk of exposure and isolating anyone who tests positive will help prevent spread among humans. Even if it were to happen, we have treatments and preventive measures, including that vaccine. “At this point, there is no reason for the public to panic,” Dr. Kang confirmed. She advises paying attention to updates and “following whatever the health officials instruct us to do.”