Recent studies of the primary documented case of the H5N1 virus passing from birds to cows — after which from a cow to a person — have generated lots of press in an age of fear about ailments “spilling over” from wildlife to agricultural animals and people. Dr. James Lowe, a professor of veterinary clinical medicine on the University of Illinois Urbana-Champaign, research the elements driving viral transmission to, and amongst, cattle. He spoke with News Bureau life sciences editor Diana Yates concerning the latest findings.
How does an infection with the H5N1 “bird flu” virus unfold amongst birds, and the way would possibly a chicken transmit the virus to a mammal?
The H5N1 virus shouldn’t be a respiratory pathogen in birds. Instead, the virus is transmitted by ingestion of fecal matter from one other contaminated chicken, so it’s an oral-fecal route of transmission. We don’t know the way the virus passes from birds to mammals. The principle is that the contaminated cows have been uncovered to contaminated birds and their feces. That’s the almost certainly clarification. We additionally don’t know the way the virus is transmitting between cows.
Scientists hypothesize that cows are uncovered to the H5N1 avian influenza virus by means of contact with the feces of contaminated wild birds.
Photo by Fred Zwicky
How critical is the an infection amongst birds, cows and different mammals?
There are extremely pathogenic and fewer pathogenic strains. The “high path” strains of avian influenza kill poultry and a few wild birds. The “low path” strains don’t end in excessive mortality amongst birds.
We don’t know the mortality fee in marine mammals like seals and sea lions as a result of we don’t know what number of of those animals have been contaminated. But 1000’s of marine mammals have died with H5N1 an infection. In these animals, and in carnivores like foxes and cats, the illness causes neurological moderately than respiratory issues. Viruses within the mind are sometimes related to extreme illness and excessive mortality.
In cows, the illness seems to be self-limiting. Many cows could also be contaminated however not affected —that’s, the an infection is undetectable or causes solely delicate illness.
In people with wholesome immune programs, an infection with the H5N1 virus could also be related to delicate respiratory issues, conjunctivitis, gastrointestinal issues or no signs in any respect. In those that are extra vulnerable, it might trigger extreme respiratory misery and even demise. To date, human mortality on account of chicken flu an infection is extraordinarily low.
Since 2006, when H5N1 was first detected in China, we aren’t conscious of any person-to-person unfold of the virus within the U.S. and such circumstances are extremely rare around the globe and are usually short-lived. Most such circumstances occurred solely after extended shut contact with an contaminated person.
While H5N1 an infection has repeatedly been discovered amongst wild birds the U.S., only two people in the U.S. have so far tested positive for the virus. The most recent case concerned somebody who labored carefully with contaminated cattle. A 2022 case was linked to publicity to contaminated poultry.
Why does the virus have an effect on so many species so otherwise?
The virus interacts with particular sialic acid receptors on the surfaces of cells, and people receptors could also be extra prevalent in numerous elements of the physique in numerous teams of animals. In marine mammals and a few carnivorous mammals, the virus migrates to the mind to bind to SA receptors there, inflicting harmful illness. In people, the affected receptors are most ample deep within the lungs. That’s why H5N1 an infection typically causes pneumonia in people. In cows, the receptors could also be extra widespread in different elements of the physique.
Is the truth that chicken flu is now infecting cows a trigger for fear a few new pandemic of chicken flu in people?
I can’t inform the long run, however there’s no indication at current that this may occur. Humans have been uncovered to chicken flu in chickens for a few years and we didn’t actually see many human circumstances there.
There’s some evidence that human publicity to different influenza viruses or flu vaccines enable the grownup immune system to raised acknowledge the risk, so there could also be some cross safety there.
But RNA viruses change constantly. And in the event you get too assured, that’s while you look actual dumb. I do know the general public loves certainty. And we’d prefer to say issues with certainty. But we in all probability know so much lower than we’d prefer to know.
