"Last week, officials announced that HPAI [highly pathogenic avian influenza virus A(H5N1)] infections had been detected in cows on several dairy farms across five states. We then learned that cows in other states got sick once transported from the original farm, suggesting cow-to-cow transmission. This marks the first HPAI infection in cows in the United States.

Yesterday, news was released that a person in Texas was infected with HPAI after working closely with the cows. 

What we know

• Lab scientists analyzed the virus that infected the cows and found: 
  • It’s the same exact virus that is infecting birds, which suggests it jumped from bird to cow.
  • We are very familiar with this virus. So much so that we know where it would need to mutate to spread better from human to human. Based on preliminary analysis, the virus has not mutated in a key spot, which is great news. 
• The person infected had very mild symptoms—eye inflammation—and is on antiviral medication. This is good news, as the few cases of human HPAI on record have tended to be severe.
• A cow isn’t a pig, which is great news. Pigs are dangerous hosts for HPAI because they have avian and human receptors. They are known as “mixing vessels” for influenza viruses. As far as we know, this is not the case for cows.
• We have well-established flu vaccine pipelines and some stockpiled materials to make a matching human vaccine quickly, if necessary. We also have antivirals that can help prevent infection and severe illness. 

What we do not know

Three main questions scientists are trying to answer: 

1. Did the virus mutate to become better adapted to cows? This will require more studies, which are already underway. 
2. Where else is it? Only a few farms are affected right now. However, viruses spread. The impact on milk supply and prices in the future is unclear. 
3. Is the virus able to transmit onward from here? It would not be surprising if there were more human cases in people who had direct contact with cows. What we don’t know is if the virus will be able to transmit onward to other humans. For example, in the latest case, we don’t know if any of the person’s contacts became infected. Epidemiologists will closely track this."

Other News sources: 

New York Times

Science

CIDRAP

Washington Post

Wall Street Journal

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