CDC issues documents on identifying, reporting novel influenza viruses

In response to the recent confirmation of influenza infections with a novel variant of the H3N2 virus, the U.S. Centers for Disease Control and Prevention issued a new set of documents to advise healthcare workers on identifying and reporting new cases.

On December 23, the CDC confirmed two additional novel flu infections, including one in a West Virginia child with a swine-origin H3N2 reassortant strain that includes the M gene from the 2009 H1N1 virus, according to CIDRAP News.

The newly-confirmed H3N2v case brings the total seen in the United States to 12 so far.

The CDC also recently confirmed an infection involving a swine-origin H1N1 variant that has acquired the M gene from the 2009 H1N1 virus. The patient, an adult from Wisconsin, had occupational exposure to swine and is the first known case of the H1N1v strain in humans.

At the same time the CDC confirmed the two new cases, it released new guidance to help prevent seasonal and H3N2v in healthcare settings. The guidance on H3N2v is considered interim in nature and consists of recommendations for specimen collecting and testing, as well investigating potential new cases.

Most of the confirmed H3N2v infections have been mild - only three of the 12 have required hospitalization, CIDRAP News reports. The CDC said it is unsure as to whether the strain will become more commonplace but warned that it is possible that healthcare providers may see additional cases.

There is no evidence that H3N2v transmission differs in any way from seasonal flu, so the CDC advises the use of the same infection control procedures already in place. The seasonal influenza vaccine may provide limited protection against the variant in adults, but no protection in children.

Because human-to-human transmission of H3N2v is occurring, the CDC's guidance aims to streamline its detection and investigation capabilities. It also recommends that states increase the number of respiratory specimens from patients with flu-like symptoms who fall into high-priority groups, including children.

The agency urged health departments to notify the CDC of all probable and suspected cases of H3N2v within 24 hours of identification.