The World Health Organization on Friday urged governments to prepare for a second wave of swine flu this fall, estimating that as many as 2 billion people could become infected over the next two years.
That's about one-third of the world's population. The WHO has stressed that most cases are mild and require no treatment, but the fear is that a rash of new infections could overwhelm hospitals and health authorities, especially in poorer countries.
WHO Western Pacific director Shin Young-soo predicted many countries may see swine flu cases double every three to four days for several months until peak transmission is reached.
"At a certain point, there will seem to be an explosion in case numbers," Shin told a symposium of health officials and experts in Beijing. "It is certain there will be more cases and more deaths."
While areas in the southern hemisphere such as Australia appear to be experiencing flu seasons not much more severe than average, it is in developing countries where the fast spread of swine flu poses the greatest threat.
In those countries, it will place underequipped and underfunded health systems under severe strain, Shin said. Governments must do what they can now to prepare their health systems, said Shin.
"We only have a short time period to reach the state of preparedness deemed necessary," Shin said. "Communities must be aware before a pandemic strikes as to what they can do to reduce the spread of the virus, and how to obtain early treatment of severe cases."
In a video address to the symposium, WHO chief Margaret Chan also warned: "We cannot say for certain whether the worst is over or the worst is yet to come."
"We need to be prepared for whatever surprises this capricious new virus delivers next... constant random mutation is the survival mechanism of the microbial world," she said
She reminded that pregnant women face a higher risk of complications. The virus also has more severe effects on people with underlying conditions such as asthma, heart disease, diabetes, autoimmune disorders and diabetes.
Chan said the issue of how to ensure adequate vaccine supplies worldwide needed to be tackled "head on."
"We need to gather advice on priority groups for initial protection," Chan said.
"This is one of the most difficult decisions governments around the world will need to make, especially as we know that supplies will be extremely limited for some months to come."
WHO urges restraint on use of Tamiflu
The World Health Organization also offered new advice to doctors Friday on the use of antiviral medications such as Tamiflu, saying otherwise healthy with mild to moderate cases do not need the medication.
Those at risk for complications from swine flu -- children younger than five years old, pregnant women, people over age 65 and those with other health problems like heart disease, HIV or diabetes -- should get the drug, WHO said.
The agency also recommended that all patients who develop worsening cases, with breathing difficulties, chest pain or severe weakness, should get Tamiflu immediately, perhaps in higher doses than now used.
The advice contradicts some current government policies, particularly those in England. There, the health agency has been liberally handing out Tamiflu to anyone suspected of having the infection.
By contrast, Tamiflu is given in Canada only to those with severe cases or when the patient is at a great risk for complications.
But in Britain, where stockpiles of Tamiflu are more plentiful than in Canada, residents can call a national hotline to get Tamiflu without seeing a doctor. It is given out by call centre operators who have no medical training. Scotland, Northern Ireland and Wales decided not to participate in the swine flu phone line.
Some experts have criticized the approach, warning it increases the chances of resistant strains emerging.
Flu expert Hugh Pennington of the University of Aberdeen has called the strategy "a very big experiment" and said England's approach was out of step with the rest of the world.
So far, only a handful of cases of Tamiflu-resistance in swine flu have been documented, including one in a Quebec man. But there has been widespread drug resistance in other H1N1 strains that are not swine flu.
With reports from The Associated Press
