The death toll from swine flu in Mexico rose to 149 on Monday, with 20 of the victims confirmed to have died from swine flu.

Perhaps more alarming, it is reported most victims were aged 20 to 50 and in good health. It is a classic scenario for the development of an epidemic, so no wonder the World Health Organisation issued a phase 4 alert, meaning a significant risk of a pandemic, or an epidemic on a grand scale.

In Mexico City, all schools, public events, cinemas and churches are closed, although people were still going into work on Monday.

But the situation is changing rapidly. The first case in Mexico was only reported on April 13 and a nationwide alert only issued last Thursday. This featured in some news reports in the UK on Friday, but really only came to prominence on Saturday.

Tourists have been advised to avoid Mexico City, the centre of the outbreak. But so far the tourism area of Yucatan has remained free of the flu.

Out on the Pacific coast in the resort of Acapulco the majority of people appear unfazed by what is happening. The images of crowds in face masks in Mexico City could be from another place. No one is wearing them here.

But there have been cases of the flu in Oaxaca, next door to the state of which Acapulco is part, and the schools, restaurants and bars are all closed. The death toll is sure to go on rising for some days whatever course the outbreak subsequently takes. And we may not know that for some time.

Travel is bound to be affected. At the moment the crisis has a feel similar to the SARS outbreak in south east Asia in 2003, when travel to Singapore and elsewhere in the region went off a cliff. Yet the crisis was contained. That might yet be the best we can hope for with swine flu.