A measles epidemic is spreading, especially among people in their teens and 20s, forcing weeklong closures at 29 universities and 22 high schools nationwide between April 1 and May 26.

With the outbreak showing no signs of letting up, the government is urging citizens not immune to the disease to get vaccinated and asking pharmaceutical companies to provide more vaccines.

Here are some questions and answers about the recent outbreak:

How many people in their teens or 20s have been infected with the disease this year?

While there is no comprehensive head count on measles patients, a nationwide survey of about 450 medical institutions conducted by the National Institute of Infectious Diseases found 286 people aged 15 and older had contracted the disease as of May 20, the second-highest number since 2001, when 368 cases were recorded by that date.

As for child patients, about 3,000 pediatric medical institutions had handled 907 cases by that date. This figure is roughly one-tenth the rate seen in 2001, according to the institute.

Infants and small children are most susceptible to the measles virus. Why did so many young people contract the disease this year?

Major measles epidemics used to occur frequently until the 1970s, and most people in their 40s and older who had contracted the disease in their youth were immune.

In 1978, the government introduced a mandatory measles vaccination program for preschoolers. However, the mandatory vaccinations were stopped when the law was revised in 1994. Nevertheless, vaccination rates have remained high, at around 90 percent, according to an institute official.

Vaccinations have reduced major outbreaks of measles among children. However, some people, even though they were vaccinated, lose their immunity over a period of 10 to 15 years if they do not boost their immunity by coming into contact with the virus. As Japan had not seen a major outbreak of measles for five years, people currently in high school and university are now more susceptible to the disease, the official said.

In addition, about 5 percent of people who have been vaccinated fail to become immune to the disease.

These people are susceptible to infection when they became older. If they go to school without knowing they have the disease, it can spread to other young people who were raised in a similar situation.

How does the disease spread and what are its symptoms?

Highly contagious, measles is spread through airborne transmission from person-to-person via cough droplets or physical contact.

Infected people exhibit such symptoms as cough, fever and rash following an incubation period of about 10 days. The symptoms persist for three to four days. Because there is no specific treatment for measles, the infected person relies on rest until the symptoms disappear.

In some cases patients develop complications, including pneumonia, encephalitis and otitis media, an inflammation of the middle ear.

What steps can people take to avoid becoming infected?

Anyone who has never been vaccinated or had the disease should get vaccinated, and the cost may be around 8,000 yen.

According to the health ministry, as of May 29 there was a stockpile of vaccine for about 90,000 people. The ministry recently announced that additional stocks to cover about 500,000 people will be supplied by pharmaceutical companies by the end of this month.

What can be done to stop a measles epidemic?

In April 2006, a new government ordinance was passed asking parents to have their children vaccinated twice — once at age 1 and again between the ages of 5 and 7, or before entering elementary school.

This method of two vaccinations has proved effective in many developed countries, including the United States and South Korea.

In Japan, the National Institute of Infectious Diseases estimates there are roughly 100,000 to 200,000 who contract measles annually. Dozens of people die of the disease, although the level has been drastically reduced compared with 50 years ago, when several thousand people died.

What’s the measles situation overseas?

Every year about 20 million people, mainly children, contract the disease. In 2005, there were 345,000 measles-related fatalities, according to the World Health Organization.

However, in many developed countries, which have taken eradication measures, the disease is now rare.

According to the WHO, in 2004 it received reports of only 37 measles cases in the U.S. In 2005, there were six reported cases in South Korea and 79 in Britain.

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