BBC NEWS | Americas | Warnings as swine virus spreadsThe United States and the European Union have urged travellers to Mexico to exercise caution, amid concerns over the spread of the swine flu virus. Mexico fears the virus has claimed as many as 149 lives there. Cases are also confirmed in Canada, the US and Spain. Secretary of State Hillary Clinton said the US - which has 40 confirmed cases - was taking the issue "very seriously". World Health Org
