Called highly pathogenic avian influenza, the H5N1 avian influenza virus that is making headlines in Michigan and the United States gets its name because it is highly adapted to infect and kill birds. H5N1 has been circulating in the United States since January 2022 and worldwide since 2021.
What worries scientists and researchers, however, is that the virus is increasingly spreading to infect other animals, such as seals and raccoons, bobcats, foxes, cows and alpacas – and now, even humans – and that we know little about the extent of its spread. infections really are.
Screening for H5N1 infections is voluntary. Farmers are not required to test their cows and people with symptoms are also not required to get tested.
There were only three known human cases of the virus among farmworkers in the United States this year – two in Michigan and one in Texas.
All three suffered mild illness and fully recovered, but some scientists worry that the more the virus spreads, the more likely it is to mutate to better infect people, which could make humans sicker and trigger a outbreak of a new flu that This could recall the early days of the COVID-19 pandemic.
One tool that can be used to assess the extent of spread of the virus in a community is to test wastewater.
That’s exactly what WastewaterSCAN, based at Stanford University, did. It monitors infectious diseases in wastewater treatment systems and, earlier this month, publicly released H5 influenza A virus test results on samples from 38 of the 50 states and the District of Columbia dating from May 21.
It found that levels of H5 influenza virus in Michigan wastewater were high at all sites tested, even in places where there are no infections among cattle herds, such as cattle processing plants. sewage from Jackson and Warren.
What does wastewater testing mean for H5 avian flu?
Testing sewage for viruses often gives the first clue of widespread infection in a specific area. But without more precise and refined testing, samples from a sewage plant with a large watershed don’t reveal exactly where the virus came from or whether it’s people or cows, other creatures (or all) who are infected. .
Virus particles detected in wastewater could come from runoff from cattle farms with infected cows or other animals, from the discharge of untreated milk into the sewage system of production facilities, or from the feces of sick people.
In WastewaterSCAN testing, only six states had detected the virus in wastewater – California, Idaho, Iowa, Minnesota, Michigan and Texas – as of Monday. Among them, Michigan was the only state with high levels detected at each of its six testing sites: Ann Arbor, Jackson, Jenison, Mount Pleasant, Traverse City and Warren.
Although Jackson County has not yet identified any infections among dairy cattle with the H5N1 influenza A virus, the largest number of positive wastewater samples, 10, have been identified at the plant wastewater treatment plant in the City of Jackson between May 21 and June 9.
The City of Warren Wastewater Treatment Plant had the second highest number of H5 influenza detections in wastewater samples statewide, with five identified between May 21 and June 11, but Macomb County also has no known outbreaks in dairy cattle.
More:Scientists try to solve the mystery of bird flu: why there are so many viruses in Michigan sewage
What are the symptoms of bird flu?
The current strain of the H5N1 virus, which belongs to the 2.3.4.4b subtype, has so far caused mild symptoms in known human cases, according to the US Centers for Disease Control and Prevention, such as eye infections , cough and runny nose.
Here are the details of the human cases known so far:
- A Texas farmworker who was exposed to sick cows in March contracted the H5N1 virus. The worker had only one symptom: eye redness suggestive of conjunctivitis or conjunctivitis. The person was treated with an antiviral flu medication, asked to self-isolate to prevent possible spread of the virus, and recovered. This is the first known case of cow-to-human transmission in the United States.
- A Michigan farm worker exposed to cows infected with the H5N1 virus was splashed in the eyes with untreated cow’s milk. In late May, he also developed an eye infection and made a full recovery, said Dr. Natasha Bagdasarian, Michigan’s medical director. This is the second known case of cow-to-human transmission.
- A second Michigan farmworker developed upper respiratory symptoms, including a cough without fever and eye discomfort from watery discharge, after working closely with infected cows on a separate farm in late May. This person has also fully recovered. This is the third known case of cow-to-human transmission.
- In April 2022, a Colorado farm worker who was slaughtering poultry suspected of being infected with the H5N1 influenza virus reported feeling fatigue for several days. The person tested positive for the virus and was isolated and also treated with antiviral flu medication. This was a case of bird-to-human transmission.
How does bird flu affect animals?
The current H5N1 strain is almost always fatal in poultry, but produces a range of puzzling symptoms in other animals.
In cows, this type of bird flu appears to infiltrate the mammary system. High levels of the virus have been detected in their milk, slowing production and sometimes causing thick, curdled milk. The cows have fevers and are not eating or drinking as they should. Sometimes pregnant cows miscarry.
Barn cats that drank raw milk from sick cows were also infected with avian flu and developed neurological symptoms, eye and nasal discharge; many died. Fox pups have also been reported to exhibit neurological symptoms when they become infected with the H5N1 virus, including tremors, blindness and lethargy, before dying.
More:Bird flu has spread to cows and milk – and experts fear a human outbreak could be next
Are my pets safe from bird flu?
It depends on the animal. Of course, birds are at high risk for the virus and can contract it through exposure to other infected birds – wild or domestic – or their droppings, mucus or saliva.
Cats are also extremely susceptible to H5N1 avian influenza and are at risk of developing neurological symptoms and death. New research suggests that ferrets also become extremely ill and can die from the virus.
Although dogs can be infected with H5N1 avian flu, cases of illness in dogs are rare. When they do get sick, symptoms are mild, the CDC reported earlier this month.
Vets are urging pet owners to make sure their cats and dogs do not chase birds or scavenge carcasses of birds or other animals to avoid the risk of infection. They should also avoid contact with other infected animals, such as cows, poultry and unpasteurized milk.
Is it safe to drink milk and eat eggs and beef?
Studies conducted so far by the U.S. Food and Drug Administration suggest that pasteurized milk and dairy products are safe to eat and drink, as are fully cooked meat and eggs.
In one out of 109 beef samples analyzed in late May by the U.S. Department of Agriculture’s Food Safety and Inspection Service, H5N1 virus particles were detected in muscle tissue. In ground beef inoculated with high levels of the virus, cooking it to at least 145 degrees (medium) or 160 degrees (well done) killed the H5N1 virus.
“Even cooking hamburgers at 120 (rare) degrees, which is well below the recommended temperature, significantly inactivated the virus,” the USDA reported.
And although similar tests on commercial milk revealed fragments of the H5N1 virus, these particles were inactivated by pasteurization and could not cause infection. However, raw milk from infected cows has been shown to pose a risk of infection.
Will my annual flu vaccine protect me from this virus?
As scientists work to develop a flu vaccine that could work against the current strain of the H5N1 virus, the CDC reported Friday that analyzes of blood samples suggest Americans have “extremely low population immunity , or even zero” against the strain of the H5N1 virus which is currently circulating. Seasonal flu vaccines do not appear to produce antibodies against the virus.
This means that “most of the population would be susceptible to infection with this virus if it began to easily infect people and spread from person to person,” the CDC said.
Contact Kristen Shamus: kshamus@freepress.com. Subscribe to the Free Press.