A WHO official reiterated yesterday there is still no evidence that a new strain of avian influenza is passing in a “sustained” fashion from person to person, despite fears that some family members may have infected one another.
“Right now we do not see evidence of sustained human-to-human transmission,” Keiji Fukuda, the WHO’s assistant director-general for health security and environment, said at a press conference.
However, he added that officials “are always worried whether there could be person-to-person transmission.”
Chinese health officials have acknowledged so-called “family clusters,” where members of a single family have become infected with the H7N9 virus, but have so far declined to put it down to human-to-human transmission.
Commenting on the clusters, Fukuda said that, based on available evidence, “it is not clear why we have these cases.”
He said families with multiple infection may have caught it from animals, the environment or one another.
Experts differentiate between “sustained” human-to-human transmission and cases in which family members or medical personnel become infected.
Fukuda spoke as a WHO team wrapped up a visit to Shanghai, the center of the outbreak in China that has killed 20 people, as part of an investigation into how the H7N9 virus is spreading.
Since announcing on March 31 that the virus had been discovered in humans for the first time, the Chinese Ministry of Health on Sunday confirmed a total of 102 cases in Shanghai, Beijing and four provinces.
“There has been no discovery of evidence of human-to-human transmission,” the ministry said in a statement.
Experts fear the prospect of such a virus mutating into a form easily transmissible between humans, which could then have the potential to trigger a pandemic.
WHO representative in China Michael O’Leary on Friday said the purpose of the 15-member team’s week-long visit was to study whether H7N9 was spreading among humans.
“The primary focus of the investigation is to determine whether this is in fact spreading at a lower level among humans, but there is no evidence for that so far except in these very rare instances,” O’Leary said.
The son of a man who was Shanghai’s first case of H7N9 was confirmed to have contracted the virus after an initial test ruled it out, officials said last week.
The Shanghai government also said the husband of a woman confirmed with the virus had become sick, but there was not enough evidence to verify transmission between them.