CDC launches extensive investigation into M infection with avian influenza
WASHINGTON — The Centers for Disease Control and Prevention should have results later this month on how a Missouri resident who had no contact with infected animals or food became infected with highly pathogenic avian influenza.
Demit Daskalkakis, director of the Centers for Disease Control and Prevention’s National Center for Immunization and Respiratory Diseases, said in a phone call with reporters Friday that the agency is investigating the bird flu case and provided more detail.
“As we previously reported, CDC will be able to partially sequence the H5 avian influenza virus in the Missouri case, despite barely detectable levels of viral RNA in patient samples,” Daskalakis said.
The process is complex and time-consuming, in part because the amount of virus in the patient’s body is so small when the test is performed.
Another contributing factor, he said, is that “the virus has two potentially important mutations, implying two amino acid differences, compared to viruses previously characterized in this event that may affect antigenicity.”
Daskalakis explained that antigenicity refers to someone’s ability to produce “a specific immune response, such as the production of specific antibodies.”
He said both the mutations and the small sample size pose challenges for the CDC, but the agency expects to release test results later this month after completing the complex lab process.
Two cases in California
missouri case This is the only diagnosed case of avian influenza in the United States this year without direct contact with infected poultry or dairy cows.
Of the 16 patients diagnosed with the H5N1 virus this year, the remaining cases had direct contact with farm animals, with 9 cases related to poultry and 6 cases related to dairy cows.
One case was confirmed in Texas, two in Michigan, two in California, and 10 in Colorado.
Public health officials emphasized on the call that the risk to the population remains low and that several studies conducted by the U.S. Food and Drug Administration indicate that pasteurized dairy products, as well as other foods, are still safe to eat.
Since February, the CDC has tested more than 50,000 samples “that have detected influenza A, H5 or other novel influenza viruses,” Daskalakis said.
He said the Missouri case was the first case of avian influenza detected through the influenza surveillance system.
Daskalakis said public health officials at the state and federal levels have been trying to determine how the Missouri patient contracted the virus through a series of “intensive interviews.” Patient’s identity.
That’s how they learned that someone living in the same house was sick and also experiencing symptoms of various gastrointestinal issues.
Daskalakis said the simultaneous onset of symptoms meant “common contact, not person-to-person transmission,” before stressing that the second person never tested positive for the virus and was therefore not considered a case of bird flu.
“At the time of the interview, the household contact had also fully recovered and had not been tested for influenza during their illness,” he said. “To be clear, there has only been one case of H5N1 influenza identified in Missouri.”
Daskalakis said that because people who lived in the same house as the Missouri patient had been asymptomatic for more than 10 days when interviewed by public health officials, “acute influenza testing of contacts is of no use.”
Instead, Missouri officials collected blood samples from the two men so that the CDC could test for “H5 antibodies to assess possible exposure to the virus,” he said.
A separate investigation was conducted at the hospital where the Missouri patient was diagnosed to determine whether any health care workers were infected with H5N1.
Of the 118 health care workers who interacted with patients in some way, 18 had higher-risk interactions before the patient was diagnosed and began using what Daskalkis called “droplet precautions.”
He said six of the health-care workers later developed respiratory symptoms, but only one of them was symptomatic by the time the public health investigation began.
He said one of them had a negative acute influenza PCR test result and the other five health care workers had recovered and did not require PCR testing.
“Because exposure can only be assessed retrospectively, Missouri also collected blood samples from these individuals for antibody or serology testing at the CDC to look for any evidence to support that their symptoms were related to their interactions with patients. “Although the risk is low, this test is important to complete the public health investigation into this case. “
The CDC began serological testing after receiving samples from Missouri in mid-September, although the complex process likely won’t be completed until later in October.
“In order to get a conclusive serology test, you need to use a virus that is genetically identical to the one obtained from the human case in Missouri, otherwise there is a risk of false negative tests,” Daskalakis said. “Since this H5 virus cannot Recovery, we couldn’t culture it because there weren’t enough Missouri samples.”
He explained that the CDC had to “use reverse genetics to make the right virus for testing to match the virus from Missouri so that we could use it in these serology tests.”
“We realize that people, including all of us at CDC, are eager to see the results of this test,” he said. “The CDC is moving very quickly while conducting rigorous scientific research to ensure the validity of these results.”
Poultry and dairy cases
In addition to human cases, avian influenza continues to infect poultry and dairy herds in the United States.
While the poultry industry has years of experience providing workers with personal protective equipment and culling affected farms, the dairy industry has had to figure out how to deal with the virus this year.
Colorado’s mandatory bulk milk tank testing program, which began in July, provides a promising case study in eliminating the H5N1 virus from farms across the country, Eric Deeble, USDA’s undersecretary for marketing and regulatory programs, said in a conference call Friday.
“Initially, this indicated significant local prevalence, with approximately 72 percent of the dairies concentrated in Weld County,” Deeble said.
But he said that after months of hard work by farmers and public health officials, only one of Colorado’s 86 dairy herds has been affected by the H5N1 virus.
“The state’s mandatory surveillance allows for ongoing monitoring of the herd and helps detect any non-negative results early, ensuring timely intervention,” Dibble said. “Even in the absence of a vaccine, the reduction in cases in Colorado gives us further confidence that H5N1 can be eliminated from swine herds across the country, even in places where we initially saw rapid increases in cases.”
USDA data shows that in the past month, three dairy farms in Idaho and 53 dairy farms in California Tested positive for H5N1.
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