Mexican people have a tradition of greeting each other with handshakes and kisses on the cheek. But recently, the government asked people to stop doing this. They have also closed schools and museums, and advised people to stay at home.   This is to stop people from catching an infectious (传染性的) disease, swine flu (猪流感). The disease has spread over the country in the past month. It has killed 159 people and caused 4,000 to become sick.  

    What is swine flu? Swine flu is a disease that causes illness in pigs. It spreads to people in two ways. They catch the virus (病毒) after being with infected pigs, or they get it from an infected person.The disease spreads in the same way as human flu, through coughs and sneezes, or by touching a contaminated surface (被污染的表面) and then touching the nose or mouth. However, it cannot be spread by eating pork. People who have caught swine flu will have a fever, a cough, a sore throat and body aches. In most cases, the infection makes people unwell but their lives will not be in danger.   

    How serious is the situation?   Since swine flu started in Mexico about a month ago, it has spread to a few other countries. The US has reported 65 cases and Canada has reported 13 cases. Other countries are checking for possible cases. Last week, the World Health Organization said the flu was a “public health emergency (紧急情况)”. It says the disease could become a global outbreak.  

    A few governments around the world have advised people in their countries not to visit Mexico. Some countries have begun checking air travelers for the disease. Russia, China and other countries have stopped buying pork from Mexico, though the flu cannot be caught by eating the meat. Health experts advise people to wash their hands frequently, to cover coughs and sneezes and to stay home if they feel ill.