The number of confirmed swine flu cases worldwide rose by 88% over the weekend of 9 and 10 May, from 2500 to 5251, in 30 countries, the World Health Organization has said.

As the number of cases of A/H1N1 flu rose, the first death linked to it in Canada was announced. A woman from northern Alberta who had chronic pre-existing health problems and who had not travelled to Mexico died on 28 April.

The numbers of deaths had risen to 48 in Mexico, three in the United States, one in Canada, and one in Costa Rica.

The total number of cases in the United Kingdom rose from 39 on Friday 8 May to 65 by the time the BMJ went to press on Tuesday, and laboratory testing is under way in another 336 cases, the Health Protection Agency said.

One of the sharpest rise in cases in the past few days was in the US, which is now the most affected country in the world. It recorded a rise of around …