No new human cases of the H7N9 virus have been recorded in China for a week, national health authorities said, for the first time since the outbreak began in March.

One previously infected patient died in the week beginning May 13, the National Health and Family Planning Commission said in a statement late Monday, taking the total number of fatalities from the virus to 36.

But the number of confirmed cases was unchanged at 130. Of those, 72 have recovered and been discharged from hospital, it said, adding that no evidence of human-to-human transmission had been detected so far.

Experts fear the possibility of the virus mutating into a form easily transmissible between humans, with the potential to trigger a pandemic.

Flu viruses are often seasonal and much of China is experiencing warmer weather following the end of winter.

But the head of the World Health Organization (WHO) warned that the evolution of the outbreak was still unpredictable.

"Influenza viruses constantly reinvent themselves. No one can predict the future course of this outbreak," Margaret Chan said Monday at the World Health Assembly in Geneva.

"Although the source of human infection with the virus is not yet fully understood, the number of new cases dropped dramatically following the closing of live poultry markets," she added.

China was accused of covering up the outbreak of Severe Acute Respiratory Syndrome (SARS) that killed about 800 people around the world a decade ago, but Chan thanked authorities for their close collaboration with the WHO over H7N9.

Nobel laureate plays down flu pandemic scaremongering
Wellington (AFP) May 21, 2013 - A Nobel prize-winning scientist Tuesday played down "shock-horror scenarios" that a new virus strain will emerge with the potential to kill millions of people.

Peter Doherty, who jointly won the Nobel prize in 1996 for his work on how the immune system combats virus-infected cells, said the worst-case scenario was a new virus with a high mortality rate that was also highly infectious.

The Australian said the world experienced such a pandemic in 1918, when an influenza variant killed an estimated 50 million people, more than twice the number who died in World War I.

Doherty said it was possible such an outbreak could occur again but it was unlikely to have such devastating consequences.

"A lot of the (1918) deaths were undoubtedly due to secondary bacterial infection and, of course, we have antibiotics to treat secondary bacterial infection now," he said at a lecture at Otago University's Wellington campus.

"In the pandemic world we all look to these shock-horror scenarios -- it makes good television, there's a lot of books about these terrible infections that are going to kill us all off.

"It makes a good book, it makes it terribly scary (but) I actually think that we'll do a lot better than that with most pandemics."

Doherty said analysis of the Severe Acute Respiratory Syndrome (SARS) virus, a form of influenza which killed about 800 people, took three months when it emerged a decade ago.

The University of Melbourne-based scientist said similar work would now take just days.

"We're doing extremely well with virus diagnosis, rapid detection and all sorts of things like that, much better than in the past, so I don't think a pandemic is going to kill us all off," he said.

Doherty said the H1N1 "swine flu" which sickened millions around the world in 2009 was an example of an highly infectious strain with a relatively low mortality rate, with some 18,500 deaths reported to the World Health Organisation (WHO).

Another strain, H7N9, emerged in China in March and has a high mortality rate of 36 deaths from 130 cases, according to official data. But there is no evidence it can be transmitted from human to human.

The WHO has also since last September confirmed 40 cases of a coronavirus closely related to SARS. It has caused 20 deaths, mostly in Saudi Arabia.