By David Ferguson
Thursday, April 18, 2013
Chinese health officials are reporting that the new H7N9 strain of influenza could be making the leap from animal-to-human infections to human-to-human cases. According to Reuters, the Chinese Center for Disease Control and Prevention is analyzing “family clusters” of people who have fallen ill in hopes of understanding more about the virus.
“We are paying close attention to these cases of family clusters,” Feng Zijian, a spokesperson for the Center, said on Wednesday. “(We) are still analyzing in-depth to see which has the greatest possibility — did it occur first from avian-to-human transmission, and then a human-to-human infection, whether they had a common history of exposure, were exposed to infected objects or whether it was caused by the environment.”
Dr Zeng Guang of the the Center’s chief of epidemiology was quoted in the South China Morning Post as saying that 40 percent of patients who have contracted the virus have not had any contact with poultry or birds that could spread the disease.
“How were they infected? It is still a mystery,” he said.
The current number of confirmed infections stands at 82, 17 of whom have died.
“Further investigations are still under way to figure out whether the family cluster involved human-to-human transmission,” Feng told China Daily. “Human-to-human transmission, in theory, is possible, but is highly sporadic.”
Among the cases that scientists are studying are the deaths of a Shanghai father may have passed the virus to his two sons and another Shanghai man who may have given the disease to his wife.
The World Health Organization, which operates under the aegis of the United Nations, is sending a team of experts to China to study whether the virus has mutated into a human-to-human transmissible form. Currently, however, there is “no evidence of sustained human-to-human transmission.”
Viruses which are only capable of limited human-to-human transmission and can spread between family members through prolonged contact and intimate exposure are considered lower risk than viruses that are capable of effective human transmission, and spread through casual contact like norovirus and the flu.
The H1N1 avian virus that infected people in 2009 and 2010 was of limited human transmissibility, and as a result, caused hundreds of thousand deaths rather than millions. An avian flu that is capable of effective human-to-human transmission could potentially pose a global health emergency.