As spring weather sets in, fears of a bird flu pandemic have not materialized, and there is less cause for worry than there was in the winter. Experts say the short-term risk of a pandemic is low, but the recent appearance in mammals of the potentially dangerous avian influenza A strain, H5N1 — the bird flu virus — demands redoubling efforts to prevent its spread to humans.

As most people know, influenza is seasonal and occurs primarily in the winter, spreading from person to person through airborne droplets or surfaces. The flu has affected humankind for millennia, and in many years, a minor mutational drift in the strains circulates, beginning in the Southern Hemisphere, then moving to the Northern. This is why a reformulated flu vaccine shot is suggested nearly every year.

The most feared scenario is a major recombination genetic event — the flu virus drastically reshuffles its genes in its hosts, resulting in major changes in genetic composition. There is little population immunity to these novel strains, and this was what led to the devastating worldwide influenza pandemic in 1918 and less severe pandemics in 1957, 1968, 1977 and 2009.

Since 1996, H5N1 has been circulating in wild birds, is found in bird droppings and spreads in a manner similar to that of other flu viruses. Variants of H5N1 circulate extensively in aquatic animals such as ducks and now routinely infect domestic fowl. But the spread of H5N1 to mammals is what has caused concern. H5N1 is now present in many wild and domestic mammals, including pet cats and dogs, as well as captive zoo mammals and, for the first time, in cattle. In the past year, H5N1 spillover to humans has infected 70 people in the U.S.; about two-thirds of cases were due to human contact with infected dairy cows (the remainder through infected poultry.)

So far, most U.S. infections have been mild, with only one fatality — an elderly man in Louisiana with underlying medical conditions who had contact with a backyard flock and wild birds. Globally, over the past 30 years, about 1,000 spillover H5N1 infections have been reported, and the mortality in these cases has been as high as 50%. Fortunately, for unknown reasons, the genetic changes necessary for efficient human spread have not been present, and there is still no evidence of person-to-person spread of H5N1.

That aside, preventing a pandemic means early detection of emerging H5N1 strains: increased surveillance of viral spread and influenza infections in hospitals and intensive care units. Besides this, surveillance must occur where the virus might be present: in raw milk and food, wastewater, animal and bird die-offs, specimens from zoo animals with flu-like illnesses and veterinary settings.

The current measles outbreak demonstrates the importance of vaccination. This is another modality to prevent bird flu outbreaks, and H5N1 human and bird/cow vaccines are being developed. A universal flu vaccine for all strains is the ultimate goal and may be more feasible than a universal vaccine for COVID-19, which mutates more frequently, complicating vaccine development.

Expect egg prices to remain relatively high while infected flocks are culled. Pasteurized milk is safer than raw milk, and eggs should be cooked fully. Ask your physician about annual flu vaccination and consult online recommendations from the Centers for Disease Control and Prevention, health departments and professional societies on how to protect pets and poultry/farm workers from acquiring the virus. Those in rural areas should prevent contact between sick and well birds and animals.

If you have flu symptoms — fever, cough, cold symptoms, aches often of sudden onset — get tested for flu (a nasal or throat swab test), especially if you have underlying medical problems, and consult your physician about taking an anti-flu medication. COVID-19 demonstrated the value of home testing kits, and home testing kits for flu are available. During an epidemic, health departments should distribute these kits.

Anti-flu medications, e.g., oseltamivir (Tamiflu), remain active against current H5N1 strains. The CDC recommends anti-flu medication in any flu patients at high risk, including the elderly, those with underlying medical conditions such as diabetes or chronic lung disease, and those sick enough to be hospitalized. Treatment within two days of symptoms may shorten the course of illness. Prophylaxis is considered for close contacts of those currently infected.

In the unlikely, but possible, event of a bird flu pandemic in humans, there are other lessons to be learned from COVID-19. Strategies to keep schools open and businesses working will be essential. Vaccine distribution systems must be improved, and protecting the most vulnerable, especially those in congregate living settings and health care providers, should be a priority. Because transmission is primarily by droplets, masking the nose and mouth with hospital-quality face masks is effective at controlling the spread of flu. Indoor air quality in close-quarter venues can be improved with frequent air exchanges and air filtration.

Influenza is not like many respiratory viruses that gradually become less virulent and reach an equilibrium with their target population, as COVID-19 did. Because H5N1 affects both birds and now mammals, it has the potential to become more lethal as it mutates. The virus’s appearance in mammals should not stir panic, but we must resist complacency and strengthen public health surveillance efforts.

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Dr. Robert Weinstein is an infectious disease specialist at Rush University Medical Center. Dr. Cory Franklin is a retired intensive care physician.

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