The image is now familiar on TV screens worldwide.But, as swine flu spreads, masks are now being worn not only in the centre of the outbreak – Mexico – but also in California. With more than 60 infections, the United States has the highest number of confirmed cases after its southern neighbour. On the border, California is at the frontline of the fight against the virus. It has declared a state of emergency as a precautionary measure. As the White House asked Congress for extra cash to finance its reponse to the threat, senior officials cautioned there could be no quick fix. Rear Admiral Anne Schuchat of the Centre for Disease Control and Prevention told a Senate subcommittee hearing: “I think we really need to be prepared for a worsening of the situation and it is also important that people realise that it is more of a marathon than a sprint here.” And swine flu is on the move, with new cases confirmed as far afield as New Zealand and Israel. For now, the only confirmed deaths are in Mexico where it is feared up to 159 lives have been lost to the virus. Why it has killed so many in the country and been relatively mild elsewhere remains a mystery. Some are stocking up on essentials as the crisis intensifies. They are acting as if the country was going to war, according to resident Maria de Lourdes Arredondo. “I am not. I am just getting on with my life as normal,” she said. But schools nationwide and visitor attractions in the capital have been closed to limit new infections. While for cafes and restaurants in Mexico City, restrictions mean only takeaway food is on the menu.