When a case emerged in Minneapolis, medical sleuths rushed to trace the path of a virus that can be deadly to kids.
Hennepin County Immunization Services offered the MMR (measles, mumps, rubella) vaccine recently in downtown Minneapolis. Luke Ibs, age 15 months, got his shot from medical assistant Linette Combs, as mom Rachael Ibs of Minneapolis offered comfort.
The virus slipped into Minneapolis unnoticed on the first day of February.
Then it found its way to a day care center. And two homeless shelters. And an emergency room. Each time, it followed at least one stranger home in search of more victims.
That was the start of the Minnesota measles outbreak of 2011, according to a report published Thursday by the U.S. Centers for Disease Control and Prevention.
The account of the outbreak, which so far has sickened 13 infants and preschoolers in Hennepin County, appears in a dispatch by state investigators in the Morbidity and Mortality Weekly Report, a weekly update on disease in America.
It reveals new details of the way state and county health officials have tracked the spread of the virus as they scramble to avoid a repeat of a deadly 1990 measles outbreak that's still fresh in their minds.
The 1990 outbreak "was really very much of a wake-up call," said Kris Ehresmann, director of infectious disease control at the Minnesota Department of Health. It killed three young children in Minnesota, sickened 462 and filled up an entire floor at Children's Hospital in St. Paul.
It explains, says Ehresmann, why health officials are being so vigilant this time around.
Back then, as now, measles got a foothold in a tightly knit immigrant community in the Twin Cities that had relatively low vaccination rates. Then, it was the Hmong community; this time, the Somalis.
This year, the first clue that measles was on the loose in Minneapolis came in early March, when lab tests confirmed that a 9-month-old baby had been infected.
Officially, measles was eliminated in this country 11 years ago. But in a typical year, Minnesota may still see one or two cases, usually arriving by airplane from a part of the world where the virus remains widespread. In this case, though, the 9-month-old baby had traveled no farther than Chicago, said Ehresmann.
At that point, state health officials went on high alert. Measles is so infectious that it can linger in a room for 45 minutes after the infected person has left, Ehresmann said. It also has an uncanny ability to find anyone in a crowd who isn't already immune.
Within two weeks, three more cases were identified and state investigators set out to find out what, if anything, they had in common. They traced them back to the same drop-in day care center, and, ultimately, to the 2-year-old child who, investigators believe, unwittingly brought the virus to Minnesota.
"It's like putting together a puzzle," said Ehresmann. "But instead of having all the pieces at the beginning and figuring out how they fit together, you get pieces as you go along."
The 2-year-old had returned Feb. 1 from a family trip to Kenya, which was in the midst of a measles outbreak. On Feb. 14, a day before developing the distinctive measles rash, that child went to the day care center and infected three other children, according to Thursday's report.
Patients can take up to three weeks to get sick after contracting the virus; in the meantime, those children carried the virus to two homeless shelters, infecting four more children; and to their homes, infecting three more. Two other children caught the measles in a hospital emergency room where a sick child had been taken for treatment, investigators found.
In all, seven of the children were of Somali descent, and most had not been vaccinated because of parents' fears about the measles vaccine. Most of the other victims were infants too young to be vaccinated.
Since then, health officials have tried to stop the virus in its path -- visiting the homes of infected children, offering vaccines and a treatment called immune globulin, which can help after exposure. They've also asked some families to keep exposed children home for up to three weeks, to make sure they're not infectious. And they helped organize a Somali community forum on measles and vaccines.
So far, the count stands at 13 cases. In the meantime, state officials also identified two unrelated measles cases in adults, one of whom was infected in Orlando, the other in India.
But it's too soon to tell if the main outbreak is over, Ehresmann said.
The early symptoms of measles can seem like nothing more than a cold, she noted, until the rash appears on the face and body. "The incubation for measles can be as long as 21 days," she said. "We really can't say we're out of the woods yet."
Maura Lerner • 612-673-7384