American cows now also have bird flu – but it’s time for planning, not panic | Devi Sridhar
aVian Flu, or H5N1, is making headlines in the United States. In recent years there have been worrying signs that the disease has spread around the world – whether in chickens in Britain, sea lions in Peru or Caspian seals in Russia. This time it has been confirmed in American cows, and the World Health Organization has warned that the risk of spread to humans is of ‘huge concern’.
Although it is still early, the hypothesis is that in end of 2023one cow became infected because she came into contact with the feces of infected birds, or because she infected dead birds in the feed. This began cow-to-cow transmission, and possibly even cow-to-bird transmission. The US Centers for Disease Control and Prevention has also confirmed this one human case of H5N1 in a farm worker, which could indicate transmission from cow to human (not seen before) or from bird to human.
Since it was identified in late March of this year (meaning it spread undetected among livestock for months), the virus has been confirmed in 33 herds in eight states. Considering how contagious H5N1 is (the R number can be as high as 100 in birds – meaning each infected bird can infect 100 others – and this is still unknown for cows), and the fact that cows are asymptomatic or have mild symptoms, it is likely that the spread has spread much further across the country and may have also reached importers of American livestock outside the US. The US Food and Drug Administration also noted that this was the case traces of the virus were found in approximately one in five commercially purchased milk samples via PCR testing, detecting both live and dead virus fragments. Further testing is being conducted by the FDA to confirm that pasteurization kills the virus; Early research showed that live virus could not be grown from milk.
The risk to the general population is still considered low as H5N1 does not appear to be transmitted from human to human. Those most at risk are farm and poultry workers who stand near infected animals and get the virus in their eyes, nose or mouth, or inhale droplets from close range. However, confirmed mammal-to-mammal transmission in the US has researchers concerned, given the potential for further mutations through intermediaries such as cows, cats or pigs.
If mutations allow human-to-human spread, bird flu would become the top priority for governments around the world. The mortality rate is estimated by the World Health Organization at 52%, including young people. The US government is preparing for this scenario with a testing, treatment and vaccine plan. They confirmed at a press conference this week that Tamiflu, an antiviral drug for flu, is seen as an effective treatment and that stocks are being built up. Two vaccine candidates stockpiled in the US also appear to be a good match for this strain. We also know (all too well) that respiratory viruses spread quickly and are very difficult to contain without restrictive measures. But this is a completely different situation than SARS-CoV-2, when it took a year to develop tests, treatments and vaccines for a new virus – we are much better prepared.
The infected cows across the pond have not yet prompted a briefing or response from the British government, as it is so far seen as an American problem. import our beef largely from the Republic of Ireland, New Zealand, Germany and the Netherlands.
Unlike poultry, where even one infected bird results in the culling of the entire flock, there is no killing of infected cows. She can cost up to $2,500 all are largely symptom-free, and there is resistance among farmers to having their herds tested given the impact on their business and sales. There is no easy answer to how to contain the virus in livestock and how to resolve the tension between human health requirements and the agricultural sector. Additionally, the medical and veterinary communities are notorious for poor communication and collaboration. Prof Rebecca Katz, co-author of The outbreak atlassaid: “This is a perfect example of the importance of operationalizing A health (a unified approach to optimizing the health of people, animals and ecosystems) and collaborations between the animal and human health sectors.”
The key message is that there is no need to panic, and that this is not a repeat of the Covid-19 pandemic. The spread of H5N1 from mammal to mammal marks a step change in the development of the disease, and there is an increased risk for people in close contact with farms in the US. Even as the disease spreads among people, the US government appears to be leading the way in creating a response plan to limit the impact on lives and livelihoods. But other governments would be wise to pay attention and plan for all scenarios. To the research community trying to understand what’s happening, this seems to come out of the blue – which just goes to show how cunning and unpredictable viruses can be, and how we’re in a constant race to stay ahead of them.