Distributed via the CDC Health Alert Network
June 7, 2013, 14:00 ET 02:00 PM ET
This health advisory provides an update on the avian influenza A (H7N9) virus [H7N9] situation and includes new recommendations on who should be tested for H7N9 in the United States. This document replaces guidance published on April 5, 2013, in CDC Health Advisory 344 “Human Infections with Novel Influenza A (H7N9) Viruses." The updated guidance reflects the most current epidemiology of H7N9 cases, which indicates that almost all H7N9 human infections have resulted in severe respiratory illness; H7N9 has been found rarely among those with milder disease. For that reason, CDC is changing its recommendations for H7N9 testing: The primary changes from previous guidance are (i) a new recommendation to test only patients with an appropriate exposure history and severe respiratory illness requiring hospitalization and (ii) a request that only confirmed and probable cases of human infection with H7N9 be reported to CDC. In the previous guidance issued on April 5, CDC recommended that all persons with relevant exposure history and illness compatible with influenza, regardless of severity be tested. CDC will continue to update these recommendations as more information becomes available. The current guidance is consistent with interim surveillance recommendations by the World Health Organization for H7N9.
As of June 3, 2013, Chinese public health officials have reported >130 cases of human infection with H7N9 from 10 provinces and municipalities in mainland China and Taiwan [1, 2]. Most patients were hospitalized with severe respiratory illness and reported poultry contact prior to illness onset [2, 3]. Preliminary results from influenza-like illness surveillance suggest that H7N9 has not caused widespread mild illness in China .
Although several clusters of human infection with H7N9 have been identified in China, sustained person-to-person transmission of the virus has not been demonstrated. At this time, no cases of human infection with H7N9 have been detected in the United States, despite testing of >60 persons with respiratory illness who reported recent travel to China.
Clinicians should consider the possibility of H7N9 infection in persons presenting with respiratory illness requiring hospitalization and an appropriate travel or exposure history. Influenza diagnostic testing in patients with severe respiratory illness for whom an etiology has not been confirmed may identify human cases of H7N9.
Confirmed and probable cases of human infection with H7N9 in the United States should be reported to CDC within 24 hours of initial detection. However, state health departments are encouraged to investigate all potential cases of H7N9 infection as described below in order to determine case status.
CDC recommends the following testing practices based on the current epidemiology of H7N9 cases.
Clinicians should be aware of appropriate infection control guidelines for patients under investigation for infection with novel influenza A viruses. Click here for guidance on infection control precautions for H7N9.
Guidance on treatment of patients under investigation for H7N9 with antiviral medications, or for guidance on antiviral chemoprophylaxis of exposed contacts, click here.
1As of June 3, 2013, China was the only country where H7N9 viruses were known to be circulating in animals or where human cases have become infected. Patients with direct or close contact with wild birds or poultry, or animal settings, such as live poultry markets while traveling in these areas should be strongly considered for H7N9 testing. For more information on countries affected, please see the CDC avian influenza A (H7N9) information page.
2Contact investigation protocols for confirmed cases may supersede the recommendations described here; testing of close contacts with any level of respiratory illness may be pursued, if in the judgment of the investigators, this is warranted.
3Influenza viruses that do not typically infect humans are called "novel" influenza viruses; this includes influenza viruses that typically infect birds and swine.
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