Following the recent report of H5N1 avian influenza in cattle in the US, the CDC has now reported H5N1 infection in a person from Texas who was exposed to infected dairy cattle. This is bound to get a lot of attention. To a large degree, it’s warranted, but it’s probably going to get overblown.

The infected individual developed conjunctivitis (i.e. redness and swelling around the eyes) – that was the only clinical sign of illness, so clearly the disease has been mild in this case. The person was told to isolate and is being treated with an antiviral drug. This is the second known infection of a person with this strain of H5N1 influenza in the US (the other case was a person in Colorado who got infected with H5N1 influenza while culling infected poultry in 2022; that person also only had mild disease – just a couple days of fatigue).

I’d sum up my initial thoughts as such:

  • Not good, but
  • Not unexpected, and
  • Not something to panic about, but
  • Not something to ignore.

Not good because we don’t want people to get sick from this virus. It’s also not good because the more time this virus spends in people, the more chance it has to adapt to be better able to infect people. It also increases the risk of recombination with a human flu virus anyone gets infected with multiple flu viruses at the same time (fortunately, we’re not in peak human flu season now). Mixing viruses like that creates the potential for emergence of a new virus with a human flu strain’s ability to spread widely in people, but one against which we don’t have any population immunity to help protect us, assuming it’s different enough from currently circulating strains with which a lot of people have been previously infected or vaccinated against.

Not unexpected since we know that people can get infected with this H5N1 strain. Human infections have been surprisingly rare given the scope of infections in myriad other species around the world, but we know they can occur. More contact with infected animals means more exposure risk. It’s another reminder of the value of routine infection control practices and the need to ramp those up when there’s exposure to potentially infected animals.

Not something to panic about because panic rarely helps. More than that, it’s good that disease has been mild in this person and at least some of the other human cases. The virus is not, at the moment, able to readily infect and be transmitted between people. We have a very small number of known infections in a global ecosystem with millions of infected animals. That’s not meant to be dismissive, since this is a still a very concerning event, but it’s meant to provide balance.

Not something to ignore because of what could happen. A rare infection from direct contact with an infected animal isn’t a big deal. Adaptation of this virus to more readily infect people or recombination with a human flu virus would be a very big deal. That might not happen, or it might have occurred already and it’s just not been identified yet. We don’t know. That’s why we need to be proactive and try to control the virus in domestic animals as much as we can (we’re kind of screwed when it comes to trying to control it in wildlife), and do all we can to make sure infected people and animals do not get exposed to other flu viruses at the same time.

Time will tell. Hopefully we keep taking appropriate measures (and up our game) to better contain this virus, and keep preparing for the possibility that it becomes a new human flu virus. We should have learned these lessons from the COVID-19 pandemic, but I fear we’ve forgotten many of them already. Things like public health measures and vaccination have become so politicized that we could be starting even farther behind than we would have a few years ago if something major develops.

Another thing to ponder: Is this the first instance or first diagnosis of H5N1 in a person associated with cattle contact? That’s always an interesting question. It could be that this is the first person that’s (likely) gotten H5N1 from a cow. It’s also possible that this has happened many times and we didn’t know because the cattle weren’t known to be infected, the person’s disease was mild and, because of that, there was no testing. That kind of context is important, but is often lacking with emerging issues.