Centuries later, the Great Flu Epidemic of 1918, also called the Spanish Flu,     1     (strike) near the end of World War I. Families     2     had only just got through the war now had to bury their loved ones who had died of the disease. As a result of the war, more people were travelling and moving perhaps than ever before in history and this caused the epidemic to spread worldwide. Having killed up to 50 million people in 18 months, the Spanish Flu is believed to have been the    3     (severe) epidemic in history. More people died of the flu than died in the war. Initially, many people believed that such epidemics no longer posed a threat until very recently     4     SARS became a cause for concern.

Susana Vazquez-Torres is a fourth-year graduate student at the University of Washington who wants to someday invent new drugs     1     neglected diseases.

Lately, she     2     (think) a lot about snake bites: Around a hundred thousand people die each year from snake bites, according to the World Health Organization—and yet, she says, “the current therapeutics are not safe and are very expensive.”

Part of the problem is     3     developing new drugs for things like snake bites has been a slow and laborious process. In the past, it might have taken years to come up with a promising compound.

When Kylie     1     (treat) by Dr. Michelle Lim, one of Australia’s leading scientific experts on loneliness, she talked about her life.     2     (drive) by two children and a company, she felt that no one understood her struggles. With her hands so full, she didn’t think it was possible to feel lonely. But she discovered loneliness doesn’t only happen to people     3     are isolated. Instead, she said, it was about feeling disconnected from others.

Polio is a scary disease     1    (cause) children to lose the ability to move and walk. More than 60 years ago, it frightened parents everywhere. Tens of thousands of children     2    (fall) to the disease. Today, we don’t really need to worry about polio. In the mid-1950s, scientists came up with a special treatment to decrease the chances of getting the disease.     3     (give) to millions of children around the world, the treatment saved them all and offered them a good chance at a     4    (health) life.

An epidemic is the name given to an     1     （infect）disease that rapidly spreads to a large number of people within a short period of time-usually two weeks or less. It can     2     （cause）by several different factors, such as a virus being carried into an area, changes in the way people live,     3     increases the chances of them coming into contact with a bacteria or virus.