Medical authorities in the US are on high alert with more than 40 people in five states sickened by the new strain of swine flu.Like Britain, France and Germany, the country has advised its nationals to avoid all “nonessential” travel to Mexico. With a public health emergency declared, the United States is monitoring incoming flights from its southern neighbour. Precautions are being taken to try to stop the spread of swine flu in California where cases have been confirmed. As schools were ordered closed, President Obama said the situation was a cause for concern but not alarm. Mexico is bearing the brunt of the crisis, with up to 149 people dead and more than 1,600 infected. On the streets, protective masks have become a must-have accessory for many. As well as schools, cafes, gyms and even law courts have shut down, although Mexico City’s subway system is still functioning. While it is far from business as usual, people are getting on with their lives. Further south in Colombia, a dozen suspected cases have prompted the government to place the country in a state of “natural disaster.” Elsewhere, from Canada to South Korea, alarm bells over swine flu have begun to toll.