Ceasing transport of live birds may be key to preventing spread of H7N9 infection in humans

As of May 10, China has reported 131 confirmed H7N9 infections in humans, among whom 32 have died.

Officials from two agencies in China offered suggestions on how to stop the spread of infection in humans.

In two separate letters published online May 10 in The Lancet, it is suggested that poultry be managed properly to control the spread of influenza A (H7N9) in humans.

In the first letter, Shui Shan Lee, from Stanley Ho Centre for Emerging Infectious Diseases at The Chinese University of Hong Kong, and colleagues said that there is a need to control poultry at the farm level, possibly through massive poultry vaccination. Urban outbreaks could be prevented by banning imports or central slaughtering, they suggested.

“Unlike in Shanghai where there might have been a common source of outbreak from the market, the sequential reports of H7N9 infections in the rest of the country suggest transmissions of the viruses over a large area spanning several cities and provinces,” they said.

In the second letter, Jianguo Xu, from the State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, China CDC, Changping, Beijing, suggested that two strategies could prevent new human infections: 1) suspending farmers markets with live birds; and 2) stopping the transport for trading of live birds carrying the virus.

“This suspension can prevent new human infections in large and dense cities, like Shanghai. But, the number of infected cities has now increased, and each city has only a few patients. This is alarming,” they said.

Vaccine effectiveness

Although no decision has been made to initiate an H7N9 vaccination program in the United States, CDC recommended in a recent issue of Morbidity and Mortality Weekly Report that local authorities and preparedness programs take time to review and update their pandemic influenza vaccine preparedness plans as it could take several months to ready a vaccination program, if one becomes necessary.

Data from seasonal influenza vaccines and the 2009 A(H1N1)pdm09 vaccines provide a basis for estimating potential effectiveness ofA(H7N9)vaccines, but the numbers do not look promising, according to an Viewpoint written by Michael T. Osterholm, PhD, MPH, and colleagues published online in the Journal of the American Medical Association.

The median effectiveness reported in six studies of adjuvanted A(H1N1)pdm09 pandemic vaccines was 72%, and results of a study of unadjuvanted A(H1N1)pdm09 vaccine conducted in the United States indicated effectiveness of 56%.

“There is no reason to believe that a yet-to-be-developed pandemic A(H7N9) vaccine will perform any better than existing seasonal vaccines or the A(H1N1)pdm09 vaccines, particularly with regard to vaccine efficacy in persons older than 65 years,” Osterholm said. “… If a pandemic occurs and this epidemiologic pattern persists, a pandemic A(H7N9) vaccine, even if it includes an adjuvant, will likely have limited to modest effects on the overall morbidity and mortality from the novel strain.”

Osterholm and colleagues also said that efforts are under way to develop seed strains for A(H7N9) vaccines, manufacture clinical study vaccine lots, and conduct phase 1 clinical studies, a process the Department of Health and Human Services said could be completed within 5 months. However, actual vaccine manufacturing likely will not occur until an A(H7N9) pandemic is considered imminent, Osterholm said.

Preparing for a pandemic

CDC has recommended that public health agencies review their overall pandemic influenza plans to identify operational gaps and to ensure administrative readiness for an influenza pandemic.

“Continued collaboration between the human and animal health sectors is essential to better understand the epidemiology and ecology of H7N9 infections among humans and animals and target control measures for preventing further transmission,” according to CDC officials.

“Another influenza pandemic is inevitable,” Osterholm said. “Even with recent additional vaccine manufacturing capacity and improvements in potency testing, the global public health community remains woefully underprepared for an effective vaccine response to a pandemic.”

For more information:

• CDC. MMWR. 2013;62(18);366-371.
• Lee SS. Lancet. Early Online Publication 10 May 2013; doi:10.1016/S0140-6736(13)60949-6.
• Osterholm MT. JAMA. 2013; Published online May 9, 2013; doi:10.1001/jama.2013.6589.
• Xu J. Lancet. 2013; Published Online May 10, 2013 http://dx.doi.org/10.1016/S0140-6736(13)60950-2.

Disclosure: The researchers report no relevant financial disclosures.