Mexico is preparing for a five-day shutdown of parts of its economy in a bid to slow the spread of swine flu.
Non-essential government services will be suspended, while businesses such as cinemas and restaurants will be closed.
Mexican officials say the spread of the virus – suspected in more than 160 deaths – is slowing, but international experts are more cautious.
Globally, cases of swine flu have now been confirmed in 12 countries across three continents.
In cases outside Mexico the virus does not appear to be severe, although one death has been confirmed in the US.
The WHO has set its pandemic alert level at five – but says it has no immediate plans to move to the highest level of six.
The shut-down in Mexico covers two public holidays and a weekend.
Some factories will stop production and schools are already closed. Residents have been urged to stay at home.
But some people say they will ignore it because they cannot afford not to work.
There is also growing concern at the effect the virus could have on Mexico’s already-struggling economy.
The number of confirmed cases of swine flu infection in Mexico now stands at about 300, officials say.
Twelve people are known to have died from the virus and it is suspected in more than 160 other deaths.
Announcing the figures, Mexican Health Secretary Jose Angel Cordova said that new cases of the virus were levelling off.
“The fact that we have a stabilisation in the daily numbers, even a drop, makes us optimistic,” he said.
But Dr Keiji Fukuda, acting assistant director general of the World Health Organisation, said fluctuations were to be expected. “If it didn’t do that [it] would be very unusual,” he said.
In other developments:
• The US has announced that it will buy 13 million new courses of antiviral treatment and send 400,000 of them to Mexico
• Mexico says it will lodge a formal challenge at the World Trade Organisation demanding explanations from countries that have banned imports of Mexican pork products
• The Inter-American Development Bank said it would approve $3bn in loans to help Mexico fight the virus
On Thursday European health ministers held an emergency meeting on measures to tackle the virus, which has been confirmed in six European countries.
EU Health Commissioner Androulla Vassiliou said Europe was well prepared to handle swine flu and there was “no need to panic”.
The ministers agreed to work with pharmaceutical companies to develop a vaccine, but rejected a French plan to suspend flights to Mexico.
Several countries have restricted travel to Mexico and many tour operators have cancelled holidays.
The WHO, meanwhile, says it will now call the virus influenza A (H1N1) rather than swine flu – which it says is misleading as pork meat is safe and the virus is being transmitted from human to human.