Life has changed in Mexico City. Streets normally filled with people are empty. One of the most popular professional soccer teams recently played a game in an empty stadium that can seat more than100,000 people. It's swine   flu that has made life in Mexico City grind to a halt  . Seemingly out of nowhere, swine flu has caused confirmed deaths in 12 countries as of April 30. It has sent a wave of alarm around the world. Governments are trying to find ways to prevent further out-breaks. The World Health Organization has raised its swine flu global threat level to five out of six. People may be familiar with bird flu, but they know little about swine flu. Swine flu is a contagious  respiratory  disease in pigs. It is caused by a type-A influenza virus. Humans can also catch swine flu. The virus causes regular outbreaks in pigs, but people usually do not catch it. However, there have been cases of the virus spreading to people, and then from one person to another. The symptoms of swine flu are similar to the common flu. They include fever, lethargy  , lack of appetite, coughing, runny nose, sore throat, nausea  , and vomiting  . The high proportion of young adults among the deaths is one of several mysteries about this virus. Most of the dead had lung damage. What caused it is not yet known. The virus spreads the same way the common flu does. When an infected person coughs or sneezes around another person, the latter is put at risk. People can get the disease by touching something with the flu virus on it and then touching their mouth, nose or eyes. There are medicines to treat swine flu. Doctors suggest using anti - viral drugs. They keep the virus from reproducing inside the body. Although there are no vaccines for it now, several everyday steps can help prevent the spread of the virus: washing hands frequently; avoiding close contact with people who are sick; and avoiding touching surfaces that might have the virus on it. People may worry that they will get swine flu from eating or preparing pork. In fact, you cannot catch the virus from pork products if they have been properly prepared and cooked. Cooking food at temperatures of 71degCkills the virus. What can we infer from the passage?
At present there still aren't effective vaccines for swine flu. Swine flu virus cannot spread in the air. From now on, people can't eat pork if they want to be safe. All of the dead killed by swine flu had lung damage.