The rubella epidemic is spreading quickly, particularly in the Kanto region.

Usually limited to developing countries, the disease, also known as German measles, poses a threat to pregnant women as it can cause disorders in fetuses, including hearing impairments, cardiac disease and cataracts.

Rubella cases spiked to 2,021 from Jan. 1 to March 21, 22 times the same period last year, the National Institute of Infectious Diseases said. Tokyo had the most cases at 899, followed by Kanagawa with 259 and Chiba with 167. Nearly 80 percent of the patients were male.

Because many patients are men over 20 who were never inoculated due to a botched vaccine, the health ministry is urging those living with expectant women, especially husbands, to get a shot if they are unsure of their vaccination history.

What are the symptoms?

The major symptoms are a reddish rash, fever and swollen lymph nodes.

The rubella virus is transmitted via aerosol droplets from coughing and sneezing. The infection starts two to three days before the rash appears and lasts for five days after the rash breaks out, according to the NIID.

Symptoms in children are usually mild, but adults tend to suffer longer from the fever and rash, it said. In rare cases, complications can trigger inflammation of the brain.

Why is the disease spreading mostly among men?

Many males 20 or older grew up in a period when there were no routine measles vaccinations for boys. They were usually offered only to girls in junior high school to protect them in case they got pregnant. After realizing that limiting the shots to girls wasn’t doing anything to prevent rubella outbreaks, Japan in 1995 began offering them to all children from 1 to 7½ years old.

In 1989, the government began touting a combined “MMR” vaccine to protect against measles, mumps and rubella. But after reports of severe side effects proliferated — including some boys who died within a few weeks of getting the shots — much of the public shunned the vaccine, creating an entire generation of uninoculated people in the ’90s.

The MMR vaccine was abandoned in 1993 for a separate rubella vaccine.

In 2006, the government began a new measles-rubella (MR) vaccine regime for children that involves getting two shots to boost its effectiveness. The first is administered at age 1, and the second one year before entering elementary school.

The MR vaccine protects against rubella and rubeola, also known as red measles. Rubeola is more contagious than rubella and often causes more serious symptoms.

However, because routine vaccinations aren’t mandatory in Japan, some people didn’t get immunized.

A government survey in 2012 found that 15 percent of men and 4 percent of women between 20 and 49 lack the rubella antibody.

What are the risks to unborn babies?

A pregnant woman who contracts rubella might also infect the fetus, causing congenital rubella syndrome. This could cause the baby to be born with hearing defects or heart disease, according to the health ministry.

The chances of an unborn child developing CRS are especially high in the early stages of pregnancy, the ministry said.

A fetus has a 50 percent chance of developing CRS if infected in the first month, 35 percent in the second month, 18 percent in the third month and 8 percent for the fourth month, according to the NIID.

2012 saw five reported cases of CRS, the second-most since 10 in 2004.

As of Friday, two CRS cases had been reported, the health ministry said.

What can expectant mothers do to protect themselves?

The Japan Association of Obstetricians and Gynecologists advises expectant mothers lacking the rubella antibody to avoid crowded places until around the 24th week of pregnancy.

It also advises people living with pregnant women to get a shot if they are not sure whether they were vaccinated.

Where are the vaccinations provided and how much do they cost?

Any pediatric clinic or hospital should have the vaccine, and it is also widely available at other medical institutions. So experts advise contacting one’s local medical provider.

Although the cost varies by institution, a rubella shot usually runs around ¥6,000, and an MR shot around ¥10,000, according to the health ministry.

The ministry recommends the MR vaccine because people lacking the rubella antibody often lack immunity against rubeola as well.

The MR vaccine is also recommended as it is more available, thanks to its use in routine vaccinations, said Koji Nabae, an official at the health ministry.

Some municipalities also provide vaccination subsidies that can lessen the cost.

Should a pregnant woman get a rubella or MR vaccine?

No. The vaccine could lead to the fetus developing a disorder.

Women also should not get pregnant for two months after receiving such a vaccination for the same reason, the health ministry said.

JAOG advises women who want to get pregnant to get the rubella vaccine if they haven’t gotten their second shot yet, and to stay on birth control for two months.

If an expectant mother has been vaccinated, does this mean she won’t contract rubella?

In most cases, yes. In rare cases, however, some don’t develop immunity after vaccination. The effectiveness of the rubella vaccine is 95 percent, and if a person receives it twice, it goes up to 99 percent, the ministry said.

What about side effects?

The rubella vaccine is one of the safest so far, the NIID says.

But there have been reports of severe side effects, including cases of idiopathic thrombocytopenic purpura, an autoimmune disease that affects platelets, the institute said.

The chances of having such a severe side effect are between 1 and 3 in a million people, it said.

The Weekly FYI appears Tuesdays. Readers are encouraged to send ideas, questions and opinions to hodobu@japantimes.co.jp

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