I’m Now Worried About Bird Flu—and You Probably Should Be Too
Reading Time: 4 minutesIf it feels like we’ve learned nothing from COVID-19, it’s because … well, we haven’t., Bird flu: Why the latest H5N1 case in Michigan is a real cause for concern.
This article was republished from Sequencer with updates to reflect additional information.
Uh, guys? Are you in the right headspace to receive information that could possibly hurt you? The Centers for Disease Control and Prevention confirmed last week that a third person in the U.S. has tested positive for a highly pathogenic avian influenza virus. Like the first and second cases reported in Michigan and Texas, respectively, this Michigan resident had been exposed to cows infected with the virus while working on a farm.
The two Great Lakes State residents worked on different farms; we also know that for the first time, this third case experienced respiratory symptoms like a cough and eye discomfort. The respiratory symptoms are a cause for concern, since it means the virus could spread more easily between humans and lead to more serious illness. Besides that, the CDC press release doesn’t say much else about the farmworker, only that they are taking an antiviral, ‘isolating at home, and their symptoms are resolving.’
Of the three human cases of highly pathogenic avian influenza found in the U.S. this year, we know most about the Texas patient, since researchers quickly published a case report in the New England Journal of Medicine. That person worked on a dairy farm, and only experienced conjunctivitis (also known as pink eye) from the virus. They told officials they came into close contact with both healthy and sick cows, and reported wearing gloves but not respiratory or eye protection. Some have speculated that their infection might have been brought on by getting infected milk in their eye.
The second case in Michigan seemed similar. According to the Centers for Disease Control and Prevention, a nasal swab from the person tested negative for H5N1, but an eye swab tested positive. Furthermore, the person’s only symptoms were eye-related. It’s not clear whether this Michigan resident used the same forms of protection when working with sick cattle. But pink eye is a less concerning symptom than signs of a respiratory infection: It’s easier to come into contact with tiny droplets from a cough or a sneeze than someone’s tears. This is one of the reasons why the most recent case out of Michigan has raised scientists’ concerns. Another speaks to the severity of this person’s symptoms, since despite its name, we’re not sure how dangerous highly pathogenic avian influenza could be to humans. (‘Highly pathogenic’ refers to its effects on birds.)
I’m getting ahead of myself, of course, because I went to public health school for infectious disease epidemiology and that sometimes draws me into thinking like a hammer looking for a nail. For H5N1—or any zoonotic infection, for that matter—to develop sustained transmission in humans, the virus would need to acquire some key genetic differences. But in the classic model of zoonotic pathogen emergence, initial ‘spillover events,’ where a disease jumps from an animal to a human, give way to cluster outbreaks where people get each other sick.
I’m not calmed by the fact that these three spillover events occurred large distances apart, at three unrelated farms. This suggests that the characteristics allowing for spillover might be widespread. Nor do I feel great that we have growing evidence that farmworkers are shaping up to be particularly at risk.
Disease surveillance can only work properly when people aren’t afraid of engaging with the health care system. Immigration status, fear of retaliation from an employer, or anxiety over having to quarantine and risk losing an income source—these are all factors that complicate public health efforts. In that light, Michigan’s aggressive active surveillance program should be taken to mean that the virus might be spreading undetected in other states.
If it feels like we haven’t learned anything from COVID-19, it’s because outside of scientific circles, we haven’t. Even the welcomed public health developments, like a more robust wastewater surveillance system and rapid genetic sequencing of viral strains, represent monitoring improvements. In the absence of coordinated action, these promising advances will make little difference.
Even so, there are some concerning sides to H5N1 we haven’t seen yet, which is a relief, I guess. So far, H5N1 hasn’t been found circulating in pigs, which are more immunologically similar to humans than other livestock and harbor other flu strains that can already infect us. That’s an issue because influenza A viruses (the type H5N1 belongs to) can undergo a process called reassortment when two different viruses infect a single cell. The upshot of reassortment is that a virus lacking the genes to be good at infecting humans can very quickly acquire those tools to sustain transmission in humans.
There’s also good news and bad news when it comes to the milk supply. When the Food and Drug Administration tested milk from retail stores across 17 states last month, 1 in 5 milk samples contained fragments of H5N1 (the bad news). The silver lining is that those are fragments; pasteurization eliminates the virus and so milk is still safe to drink. Of course, that means now is probably one of the worst times to get into drinking raw milk.
Could we be making a mountain out of a molehill? Potentially, given that the CDC’s risk assessment for the general public remains low. But my fear is that we haven’t learned anything from COVID-19 and are doomed to ignore pandemic potential until it’s too late. I think that caution outweighs the risk of getting too worked up over a bird disease.
Ref: slate
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