Measles is back in Minnesota.

For the first time since 2001, a child in the state has picked up the infectious disease from someone in the community, adding one more case to what federal health officials say is a worrisome number nationally.

The Minnesota child, who lives in Hennepin County but who has not been identified, is 10 months old -- too young to have received a measles vaccine that is typically given at 12 months. The child contracted it from an unidentified person in the community, said Ruth Lynfield, state epidemiologist.

That's a rare way for the disease to spread in Minnesota, where the handful of cases in recent years have resulted after travel to areas where measles is more common.

But it fits a concerning trend nationally. Between January and July, 127 measles cases in 15 states were reported to the Centers for Disease Control and Prevention, the largest number in the past seven years. So far, no child has died. Most cases have occurred in children whose parents decided against having them vaccinated for religious reasons or because of concerns about the safety of vaccines.

If vaccination rates drop significantly, the U.S. population could lose what is called "herd immunity," meaning an infection cannot spread.

State and Hennepin County health officials are investigating who might have infected the child as well as whom the child might have infected.

The child became ill on July 29 and was in two clinics, an emergency room and around the community before being diagnosed. Health officials are warning doctors and clinics that measles is present in the community and to watch out for it.

"Measles is a significant infection," Lynfield said. "The best way to protect against getting measles is vaccination. It's important that people be up to date on their vaccine."

In Minnesota, 95 percent of children aged 19 to 35 months are vaccinated, the fourth-highest rate in the country. But health officials are increasingly concerned that as more parents choose not to vaccinate their children, major outbreaks could occur in the United States, as they have in other countries. For example, since 2006 there have been 2,250 cases in Switzerland, where vaccination rates are much lower.

The disease was once extremely common, infecting as many as 4 million people and killing as many as 500 each year. But the development of a highly effective vaccine in 1963 caused cases to plummet. In 2000, health officials declared ongoing transmission of the disease eliminated except for cases imported from other countries.

Measles is a serious, highly contagious respiratory illness caused by the rubeola virus. It is the most deadly of all childhood illnesses that present with a rash and a fever. Symptoms also include cough, runny nose, red eyes for a few days followed by a rash.

Complications can be severe. They range from ear infection to encephalitis. One to two children in a thousand die from the measles infection. Pregnant women who develop measles are more likely to miscarry, deliver prematurely or have a very low birth weight baby.

Measles is transmitted by direct contact with infectious droplets or, less commonly, by airborne spread. The incubation period of measles from exposure to rash onset is generally 14 days. Patients are usually contagious from four days before until four days after the onset of the rash.

For more information on measles, go to www.tinyurl.com/6yyrbo.

Josephine Marcotty • 612 673 7394