While the risk to the general population from the H5N1 avian flu virus remains low, an assessment rated its future pandemic potential as moderate, the same as previous assessments, said the Centers for Disease Control and Prevention. “The results of this IRAT [Influenza Risk Assessment Tool] validate the pro-active, coordinated U.S. government response,” said the CDC in a weekly report on bird flu.
The CDC, FDA, and USDA have complementary roles in responding to outbreaks of bird flu in farmworkers and in livestock. The CDC works with state public health officials to identify and treat infected workers. The FDA monitors the safety of dairy products. The USDA strategy is to isolate and eradicate the virus on the farm.
IRAT assessments are based on expert opinion of the potential for a new influenza virus variant to gain the ability for person-to-person spread and the resulting potential public health impact compared to other viruses that were previously evaluated. The virus that infected a dairy worker in Texas in April scored “in the category of ‘moderate risk’ for potential future emergence and public health impact,” said the CDC. “This is similar to previous assessments of earlier avian influenza A(H5N1) viruses.” Influenza A viruses circulate mainly among birds.
“The current risk to the general public from contemporary H5N1 avian influenza (bird flu) viruses is still considered low. The current H5N1 bird flu continues to be mostly an animal health issue,” said the CDC. “Human infections with H5N1 bird flu are rare, and these viruses are not well-adapted for spreading among people, as they do not currently have the ability to easily infect the human upper respiratory tract. Most past human infections have occurred following close, unprotected contact with sick or dead birds.”
In a letter to a medical journal, Michigan and CDC clinicians described the symptoms and treatment of two dairy farmworkers in Michigan who were infected by the H5N1 avian flu virus and cited the risk from “direct and close exposure to raw milk and secretions from infected dairy cows.”
The CDC said at least 230 people have been tested for bird flu after developing flu-like symptoms after exposure to infected or potentially infected animals. To date, 13 cases have been confirmed since April — all among livestock workers.