Bird flu spreading between humans, WHO fears
Concern over transmission among communities as girl dies and others are sent to hospital in Cambodia
‘When you have only one case, you imagine that it’s because this case was exposed to animals, either alive or dead’
THE World Health Organisation is “really concerned” that the bird flu outbreak may now be spreading between people.
The WHO has also ordered a vaccine to be made in response to the rapid spread of the strain of H5N1 avian influenza causing the current outbreak.
An 11-year-old girl died of bird flu in Cambodia this week, and her father and 11 others have also been infected.
Experts are worried the large cluster might mean the virus has now evolved to be able to be passed from one human to another.
While captive and wild birds have been killed worldwide by the H5N1 strain, there has so far been no evidence that it can pass between mammals. If the virus has been able to cross the species gap from birds to humans, then concern about bird flu’s potential to cause a pandemic will escalate.
Limited human-to-human transmission has been recorded before. In 1997, officials in Hong Kong confirmed 18 cases of H5N1, which, in some instances, spread between people. Then, the virus died out without sparking a broader epidemic.
Dr Sylvie Briand, the WHO director of epidemic and pandemic preparedness and prevention, said that the Cambodia outbreak is causing more alarm than isolated cases that have popped up in the intervening two decades.
“When you have only one case, you imagine that it’s because this case was exposed to animals, either alive or dead. So for us it means it is a zoonotic infection,” she said yesterday.
“But when you see that there are a number of potential cases surrounding this initial case, you always wonder what has happened.
“Is it because maybe the initial case has transmitted the disease to other humans? And so we are really concerned about the potential human to human transmission coming from this initial spillover from animals.
“This is [the] investigation that is ongoing in the contacts of this girl in Cambodia. We are first trying to see if those contacts have H5N1 infection and that’s why we are waiting for the laboratory confirmation of those cases.
“Secondly, once we have this confirmation, we will try to understand if those people have been exposed to animals or if those people have been contaminated by the initial case.”
WHO staff have now been deployed on the ground in Cambodia and the results of these assessments will dictate the next steps.
Dr Richard Webby, director of the WHO Collaborating Centre for Studies on the Ecology of Influenza in Animals, added that “in response to the spread of H5N1 and a little bit of evolution” a new vaccine specifically against the dominant strain is to be developed.
“We are putting another H5 candidate virus into production and that will start soon,” he said.
Dr Webby added that the current stockpile of candidate virus vaccines which could be deployed into full fledged jab drives should the animal infection be proven to have made the jump to spread among people – is also being assessed to see if it works against the dominant form of bird flu.
Evidence suggests that if the strain behind the ongoing avian pandemic did jump to people then the existing stockpile would work well against it, even if it may take six months to create the updated jab.
“There has been a little bit of work looking at some of the serum collected from people who took part in vaccine trials to some of these earlier H5 clades and several of those people worked quite well with some of the recently circulating viruses,” Dr Webby said.
“From a vaccine stockpile and response point of view, [this] is encouraging and suggests the human response to some of the vaccines does induce a broad immunity that cross-reacts with a lot of the clades we are seeing.”
Dr Wenqing Zhang, WHO Global Influenza Programme (GIP) chief, added that there are almost 20 H5 vaccines licensed for pandemic use, and the new one will add to this armoury.