Rubella, a viral infection that once caused tens of thousands of birth defects and deaths in a single outbreak, has been eliminated from the United States, health officials said on Monday.

But Americans still must vaccinate their children, and women who might get pregnant must still be sure they are immune, because the disease exists elsewhere, the Centers for Disease Control and Prevention said.

“A disease that once seriously harmed tens of thousands of infants is no longer a major health threat, thanks to a safe and effective vaccine and successful immunization programs across the country,” CDC Director Dr. Julie Gerberding told a Washington, D.C. news conference.

“We should take pride in this accomplishment, and also recognize that we must maintain our vigilance or we can see a resurgence of disease.”

The Atlanta-based CDC said that in 2004, nine rubella cases were reported in the United States, all of which originated in other countries.

“Recently, the cases we do have are not cases that have been transmitted in the United States,” Gerberding said.

Rubella, commonly known as German measles, soft measles or three-day measles, is a usually mild viral infection that causes a fever and a rash. But early in pregnancy it can cause birth defects ranging from deafness to severe brain damage and death.

“During 1964 and 1965 a rubella epidemic in the United States caused an estimated 12.5 million cases of rubella and 20,000 cases of congenital rubella syndrome which led to more than 11,600 babies born deaf, 11,250 fetal deaths, 2,100 neonatal (newborn) deaths, 3,580 babies born blind and 1,800 babies born mentally retarded,” the CDC said in a statement.

A vaccine was licensed in 1969 and since then the rubella virus has been included in the measles, mumps and rubella (MMR) combined vaccine routinely given to babies and young children.

Now the CDC estimates that 93 percent of the nation’s children under 2 get the vaccine.

And Gerberding said they should continue to do so.

“As long as there is rubella anywhere in the world, there could be rubella in our children too,” she said.

“The importance of continuing vaccination cannot be emphasized enough,” Dr. Steve Cochi, who heads the CDC’s National Immunization Program, added in a statement.

“Cases of rubella continue to be brought into the country by worldwide travelers and because of bordering countries where the disease is active.”

The Pan American Health Organization is planning a vaccination campaign this year that will include every country in the Americas and will include a rubella component.

In 1997 there were more than 130,000 cases of rubella in the Americas; in 2002 there were 8,670. Mexico had the most cases with 3,685 and Venezuela had 3,662, according to PAHO.