Perspective from Gregory A. Poland, MD
April 15, 2013
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CDC: Intense surveillance needed on H7N9 in humans and animals

Perspective from Gregory A. Poland, MD
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Intensified surveillance in both humans and animals will answer important questions about the H7N9 virus that is currently affecting humans in China, according to Timothy M. Uyeki, MD, and Nancy J Cox, PhD, both of the Influenza Division of the CDC’s National Center for Immunization and Respiratory Diseases.

“We cannot rest our guard,” they wrote in an editorial published in The New England Journal of Medicine. “The coming weeks will reveal whether the epidemiology reflects only a widespread zoonosis, whether an H7N9 pandemic is beginning, or something in between.”

So far, there have been 87 patients with laboratory-confirmed H7N9 and 17 deaths. There has been no evidence of human-to-human transmission, but more than 1,000 close contacts of those with the virus are being monitored.

Researchers from the Chinese CDC isolated a novel reassortment avian-origin influenza A(H7N9) virus from three patients who died in the outbreak in China, according to a coinciding report in NEJM. Six internal genes were from avian influenza A(H9N2) viruses.

The first patient was an 87-year-old man with chronic obstructive pulmonary disease and hypertension who presented with cough and then high fever and dyspnea. The second patient was a 27-year-old man with a history of hepatitis B virus who presented with high fever and cough. He worked as a butcher in a market that included live birds. Both patients were from Shanghai. The third patient was a 35-year-old woman from Anhui with a history of hepatitis B virus who presented with high fever and cough. She had visited a chicken market 1 week before symptoms developed.

The researchers found substitution Q226L (H3 numbering) at the 210-loop in the hemagglutinin gene in the A/Anhui/1/2013 and the A/Shanghai/2/2013 virus, but not in the A/Shanghai/1/2013 virus. In all three, they identified a T160A mutation at the 150-loop in the hemagglutinin gene and a deletion of five amino acids in the neuraminidase stalk region.

“Severe avian influenza A(H7N9) infections, characterized by high fever and severe respiratory symptoms, may pose a serious human health risk,” the researchers wrote. “We are concerned by the sudden emergence of these infections and the potential threat to the human population.”

Uyeki and Cox said severe disease in humans caused by novel influenza A viruses “is a seminal event,” and the discovery of this virus “is of major public health significance.”

For more information:

Gao R. N Engl J Med. 2013;doi:10.1056/NEJMoa1304459.

Uyeki T. N Engl J Med. 2013;doi:10.1056/NEJMp1304661.