Experts are concerned about the spread of bird flu in the U.S. as health officials try to contain the virus.
The U.S. Department of Agriculture announced last week that a second strain of bird flu had been detected in dairy cows. The D1.1 strain was previously only detected in wild poultry and birds, which indicates that it only recently spread to cattle.
Nevada soon reported its first human case of bird flu in a dairy farmer, and the Centers for Disease Control and Prevention confirmed that it was also a different strain.
D1.1 was also found to cause a more severe illness in humans. It has been linked to an extreme case in British Columbia, and to a death that occurred in Louisiana. The British Columbia patient suffered from asthma and a higher BMI, while the Louisiana patient was older and had pre-existing health conditions.
The CDC states that the risk for the general population is low, and there are currently no signs of transmission from person to person.
Experts in infectious diseases said that detection of D1.1 would lead to increased surveillance. They also raised questions about the possibility of the virus mutating.
Dr. Dean Blumberg is the chief of the division for pediatric infectious diseases at UC Davis Health. He said, “I’m concerned that multiple strains are being transmitted between birds and cattle. Then from cattle to people.” “And, the more this occurs, the higher the risk that further mutations will develop that could facilitate human-to-human transmission. And, if transmission is efficient and that happens, we may be looking at a pandemic.”
“That is the concern.” “I don’t want to alarmise you, but this is the concern,” said he.
Potential Adaptations and Mutations
Up until recently, the only form of bird flu that had been detected in U.S. dairy herds was B3.13, whereas D.1.1 was limited to migratory and poultry birds.
Dr. Benjamin Anderson is an assistant professor at the University of Florida College of Public Health & Health Professions in the Department of Environmental and Global Health. He said that this was evidence of the virus adapting.
He said that migratory birds could now more easily spread H5N1 to other areas of the country since they can now pass D1.1 on to cattle.
He said the virus could mutate each time a new case is reported, which would lead to a strain more infectious or that can be transmitted from person to person.
Anderson stated that the more the virus circulates, and the more animals are infected, the greater the number of people exposed. “There are so many opportunities for mutations to occur and eventually adaptations,” Anderson said.
Dr. Michael Payne is a researcher and outreach specialist at the Western Institute of Food Safety and Security, part of the University of California Davis School of Veterinary Medicine. He said that it was encouraging that no mutations were found in the D1.1 virus strain that affected Nevada cattle.
He said that “no mutations…were detected” which could make it easier to transmit from cow to cow or person to person. “There is no evidence of virus transmission from person to human in Nevada or any other state.”
He said that there had been no changes made to the H5, also known as the hemagglutinin portion of the virus. This is the external coating of the virus which helps it to attach to mammalian cells.
Payne stated that this was reassuring from a disease-control perspective because it increased our confidence that cows who have recovered from the “older version”… have antibodies that will neutralize the “newer version” D1.1.
Increased Surveillance
Experts believe that the U.S. should increase its surveillance and detection system now that more cases of D1.1 in humans and animals are being reported.
Blumberg stated that although the CDC recommends testing asymptomatic dairy workers, it is unclear how widespread asymptomatic infections are among dairy workers.
In a report released by the CDC on Thursday, three veterinary professionals who work with poultry and/or dairy cattle had antibodies in their blood which indicated previous bird influenza infection. The three veterinary practitioners did not report any symptoms of influenza or respiratory illness and were unaware that they had been exposed.
Blumberg stated, “I believe there are many more studies that could be done. Then getting these data and sharing them with scientists and epidemiologists as well as the public will be very important.”
Anderson stated that some states conduct more intensive surveys than others. Nevada’s health officials detected D1.1 in their state under the USDA National Milk Testing Strategy. He said that states that increase their testing will benefit the federal surveillance program.
He said: “That program was a great way to collect additional epidemiological information, but it isn’t implemented the same in all states.” “It would be great to have the capability to coordinate surveillance across states more broadly.”
