By Marie Rosenthal, MS
The CDC issued a health advisory asking clinicians and laboratories to shorten the timing for subtyping all influenza A specimens from hospitalized patients to enable faster identification of nonseasonal influenza.
The CDC said all hospitalized patients, particularly ICU patients, with suspected influenza should be tested to confirm the diagnosis. The agency wants the subtyping expedited to identify human infections with avian influenza A(H5N1). This information would support “optimal patient care and timely infection control and case investigation,” the agency said in the alert.
The accelerated subtyping is part of a comprehensive strategy to identify severe human infections with avian influenza A(H5) viruses, in addition to characterizing seasonal flu viruses faster.
Although the CDC said the risk for avian flu among most humans is still very low, “the needle has moved a little,” William Schaffner, MD, told Infectious Disease Special Edition. “More dairy herds are found to be infected, and the virus is capable of infecting more mammalian species. In addition, there have been a few more serious infections in humans.
“In response, the surveillance for possible bird flu infections in humans is being ramped up, as the health alert indicates. Quite appropriately, the CDC is asking all clinicians and laboratories to look more elaborately for bird flu, and one way to do that is to do ‘molecular fingerprinting’ on more influenza viruses,” added Dr. Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University School of Medicine, in Nashville, Tenn.
Jonathan E. Schmitz, PhD, MD, an assistant professor of pathology, microbiology and immunology, also at Vanderbilt, said this increased subtyping should not be a burden on most hospital laboratories.
“In general, this shouldn't increase clinical lab workflows tremendously,” he said. “For many labs, influenza testing for admitted patients (for whom explicit H5 testing is recommended) is a fraction of total influenza testing, which also cover outpatients” he said, and in-house H5 testing is something that few laboratories offer anyway.
“It just means that clinical labs and managing clinicians have to be very cognizant to refer specimens from hospitalized influenza patients for explicit H5 testing to refence or public health labs, if they can't identify an H3/H1 subtype in-house though multiplex syndromic PCR testing,” said Dr. Schmitz, who is also an editorial advisory member of Infectious Diseases Special Edition.
He said the alert is a reminder that non-severe human cases of avian influenza could potentially be overlooked during routine outpatient practice.
He said the alert is a reminder that non-severe human cases of avian influenza could be overlooked during routine outpatient practice. (For more about diagnosing respiratory infections from Dr. Schmitz, check out our review article in our next print issue or one of these articles on the IDSE website.)
The United States has seen outbreaks among poultry and dairy cows, as well as infections among other animals. Since 2022, 67 people in the United States have come down with avian influenza A(H5) virus infection, with 66 occurring in 2024. Most of the cases have been mild, but one fatality was reported.
