Chuck Darwin<p>The strain of flu infecting dairy cows—H5N1—is a highly pathogenic <a href="https://c.im/tags/avian" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>avian</span></a> <a href="https://c.im/tags/influenza" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>influenza</span></a>. </p><p>Scientists have been watching these viruses closely since the 1990s because of their potential to spark a pandemic. <br>In 1997, avian influenza sickened <a href="https://c.im/tags/humans" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>humans</span></a> for the first time. Eighteen people in Hong Kong became infected, and six died. <br>Small spillovers into mammals aren’t uncommon for these viruses, especially in recent years. Avian influenza has been reported in mink, skunks, raccoons, coyotes, seals, sea lions, and bears, to name a few. </p><p>But having the virus in <a href="https://c.im/tags/domesticated" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>domesticated</span></a> <a href="https://c.im/tags/mammals" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>mammals</span></a> that come into frequent contact with humans is new territory. <br>“Exactly what happens when an avian flu virus replicates in a <a href="https://c.im/tags/cow" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>cow</span></a> and potentially transmits from cow to cow, we actually don’t have any idea at all,” says Richard Webby, a virologist at St. Jude Children’s Research Hospital who studies avian influenza.</p><p>Here’s the good news: even though the virus is infecting dairy cows (and now one dairy worker), “this is still very much a bird virus,” Webby says. <br>Genetic sequencing by the USDA and the Centers for Disease Control suggests that these new infections are caused by a strain of flu that’s nearly identical to the virus circulating in wild birds. Few of the changes they did identify would allow it to spread more easily in mammals.<br>The spread of bird flu in cows is worrisome, but not as worrisome as it would be if the infections were happening in pigs, which are an ideal mixing vessel for flu virus. <br>Pigs are susceptible to swine flu, avian influenza, and human influenza. That’s how swine flu emerged back in 2009<br>—multiple viruses infecting pigs swapped genes, eventually giving rise to a virus capable of human transmission. <br>Mammalian infections with bird flu have mostly been one-offs, Webby says. <br>A mammal gets infected by eating a dead bird or ingesting bird droppings, but the infection doesn’t spread. <br>One notable exception occurred in 2022, when H5N1 popped up on a mink farm in Spain and quickly jumped from barn to barn. <br>Scientists also suspect that in rare cases, the virus has spread among family members. <br>Cow-to-cow transmission hasn’t been confirmed, but the fact that some cows became infected after the arrival of cows from affected herds suggests that it may be occurring. <br>That transmission may not be via coughs and sneezes—the traditional way flu gets passed on. It could be indirect. “So an infected cow drinks from a trough of water and the next cow comes along and drinks from that same trough,” Webby says.<br><a href="https://www.technologyreview.com/2024/04/05/1090747/new-bird-flu-infections-heres-what-you-need-to-know/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://www.</span><span class="ellipsis">technologyreview.com/2024/04/0</span><span class="invisible">5/1090747/new-bird-flu-infections-heres-what-you-need-to-know/</span></a></p>