Background and Purpose
Novel influenza A viruses are influenza A viruses that have infected people but are different from seasonal influenza A viruses that are currently circulating among humans. Novel influenza A viruses are predominantly of avian or swine origin. The clinical spectrum of human infection with avian influenza A viruses varies considerably: from asymptomatic infection to mild illness, including conjunctivitis, fever, and cough; to severe illness, including fulminant pneumonia, acute respiratory distress syndrome (ARDS) and multi-organ failure resulting in death.

This document provides interim guidance for clinicians and public health professionals in the United States on appropriate specimen collection and diagnostic testing for patients who might be infected with novel influenza A viruses with the potential to cause (or are known to have caused) severe illness in people. More information about specific novel influenza A viruses, including those that have caused illness in humans, is available here.

The spread of highly pathogenic avian influenza (HPAI) A(H5) or A(H7N) viruses in North America among wild birds or poultry might increase the likelihood of human infection with these viruses in the United States. CDC believes that the current risk to the general public’s health from avian influenza A viruses in the U.S. is low. However, because the recently detected HPAI A(H5N1) viruses are related to viruses that have caused severe disease in infected humans, they should be regarded as having the potential to cause severe disease in humans until shown otherwise. Current case definitions and recommendations for patient testing and treatment should also be consulted.

Following detection of avian influenza A viruses among US wild birds or poultry with the potential to cause severe illness in humans, CDC recommends maintaining the enhanced surveillance efforts practiced currently by state and local health departments, hospitals, and clinicians to identify people at increased risk for novel influenza A virus infection. Clinicians should notify their state health department immediately if they decide to test a patient for novel influenza A virus infection so that appropriate testing and follow up of contacts is initiated.

CDC should be notified immediately in the event that any clinical specimens from suspected patients test positive for novel influenza A virus or if the testing of clinical specimens from suspected cases are inconclusive. Human infection with a novel influenza A virus is a nationally notifiable condition.