Highly pathogenic avian influenza continues to spread throughout wild birds, domestic poultry and cattle in the United States. Other mammals, including house cats, have been infected. Seventy cases have been reported in humans since the initial outbreak, mostly among people with close contact with infected birds or cows. More than 1,000 dairy herds have tested positive for H5N1 to date. Additional herds have tested positive in recent weeks.
Amid confusion and misinformation about avian influenza, and public health in general, ID physicians play a key role in the One Health approach that’s needed to contain this disease.
- The evidence-based guidance and information we provide to the general public and the medical community are essential to an effective response to avian flu.
- As clinicians, we have patients who are farm workers, have backyard flocks, have pets or are simply worried about this emerging pathogen. We advise them on special precautions they should take based on their risk factors to reduce their chances of becoming infected.
- Health care epidemiologists like me are working through institutional protocols for the identification and isolation of patients with avian flu, while our laboratory colleagues are fine-tuning testing protocols and our research partners are developing additional treatments and vaccines.
What should the general public, patients and other physicians know about avian flu in humans?
While the overall risk to humans is low at present due to the limited ability of the virus to spread from person to person, the risk to individuals who come into close contact with animals, especially dairy cows and chickens, is greater. Since most patients have had mild illness, many cases are likely being missed, and the actual number of cases is likely much higher than reported.
- The Centers for Disease Control and Prevention has guidance for reducing the risk of exposure to avian influenza for people working with animals. Targeted toward farm workers, veterinarians, food processing workers and zoo workers among others, the guidance includes recommendations for engineering controls, administrative controls, testing, treatment, training, practices and personal protective equipment.
- People with backyard flocks and indoor-outdoor pets (like hunting dogs) should also practice caution. Humans and pets should avoid direct contact with sick or dead birds. Drinking unpasteurized milk is always discouraged due to a high risk of foodborne illness, and this advice is especially important during the current outbreak.
Physicians should be aware of local avian flu epidemiology, including the prevalence of infection among wild birds, farm animals and humans. Even in areas without affected cattle or poultry, avian influenza should be considered in a patient who has tested positive for influenza A and who has a history of animal exposure (not including indoor house pets), especially in the presence of conjunctivitis, a symptom that has characterized a large proportion of cases.
- In areas with farm animal outbreaks, the threshold for testing should be lower. Some PCR platforms automatically provide subtyping of influenza A. If a patient with risk factors for avian flu has an influenza A subtype result of “untypeable” (which means not H1 or H3), specific testing for H5N1 influenza should be sent. Testing for H5N1 is now available at several commercial laboratories in addition to public health labs.
How is the U.S. government responding to avian flu?
The U.S. Department of Agriculture announced on March 20 plans to invest up to $100 million for research on vaccines and other therapeutics for avian influenza. CDC and USDA are collaborating with state partners to conduct surveillance and contact tracing and to support mitigation efforts. Genetic sequencing by CDC and USDA labs has enabled a better understanding of the spread of the virus and its mutations.
Together, the Food and Drug Administration and USDA have been working to ensure the safety of the food supply. A stockpile of personal protective equipment, antiviral drugs and vaccine candidates is maintained by the Administration for Strategic Preparedness and Response.
Vaccination of livestock is a topic of ongoing conversation, but it is not clear that the risk-benefit ratio favors such an approach. A vaccine that provides protection against lethal disease while allowing the virus to spread could worsen the outbreak.
Government agencies have faced numerous challenges in their response to this outbreak, including the large proportion of undocumented and non-English speaking farm workers, potential adverse economic impacts and the need for complex interagency coordination at a time when the federal workforce is being reduced. All of these activities, however, are critical to the physical and economic health of our country and require ongoing federal funding prioritization.
Should farmers let avian flu spread through poultry in order to identify those birds that are immune?
Poultry experts warn that it is neither effective nor humane to let the virus, which quickly kills approximately 90% to 100% of chickens by causing multi-organ failure, spread through a flock and that this would further risk U.S. poultry populations. While it may sound gruesome, culling infected poultry is the recommended approach to stop an outbreak before it causes widespread suffering and disease and to prevent spread to other flocks.
- Even if farmers could ensure that the virus does not jump to another flock, letting the virus loose among millions of birds means millions of opportunities for mutations that might lead to emergence of a more virulent or transmissible strain. In addition, caring for a flock with such a heavy burden of infection would pose an even greater danger to farm workers.
There is little genetic variability between chickens in a flock, so surviving an avian flu outbreak is likely more related to luck than an inherent characteristic that can be leveraged for future prevention.
What is IDSA doing about avian flu?
IDSA continues to engage with federal partners and other stakeholder organizations in discussions about avian flu. Our task force on this topic, composed of IDSA members with expertise in avian influenza in humans and animals, is guiding these efforts. Our members are working to help educate the public on what they need to know about avian flu to protect themselves and their families. We are also working to keep federal health officials engaged and well informed about this virus, the resources required to combat it and the local impacts on public health.
Avian influenza may or may not become the cause of our next global pandemic. H5N1 has limited capacity for person-to-person spread in its current form, but more spread means more opportunity for mutation and recombination, and thus more risk to human health. IDSA members, as always, have responded to the call for action.
We urge our federal partners to maintain a strong and coordinated response to contain and mitigate this virus.