(CNN) A measles outbreak continues to strike Minnesota as health officials stress the importance of getting vaccinated.

There are now 48 confirmed measles cases in Hennepin, Ramsey and Crow Wing counties, mostly affecting unvaccinated Somali-American children, according to data released by the state's Department of Health on Monday.

Of those impacted, 46 are children 10 and younger; 41 are Somali-American; and 45 have not been vaccinated against the disease, according to the data.

The state's outbreak -- the largest in over two decades -- appears to have started in a Somali community, where vaccine skepticism has recently spread, said Kristen Ehresmann, director of the Infectious Disease Epidemiology, Prevention and Control Division at the Minnesota Department of Health.

"I want to be very clear that this outbreak has nothing to do with being Somali. It's just the sheer fact of being unvaccinated," Ehresmann said.

"Usually, states will see one or two cases in a year, and what's concerning is, as of today, we'll be at 48 cases of measles," Ehresmann said of Minnesota.

"The most worrisome thing is, it's a completely unnecessary outbreak," she said. "We have a vaccine that can prevent measles, and yet we're seeing this widespread transmission."

'Measles finds unvaccinated people'

Skepticism around vaccines in Minnesota's Somali community, the largest Somali community in the United States , emerged in 2008.

That's when parents started to notice a disproportionate number of Somali children receiving special education services for autism in Minneapolis, which is in Hennepin County, Ehresmann said.

"At that point, the anti-vaccine groups just really started targeting the community," she said.

Then, measles, mumps, and rubella (MMR) vaccination rates began to plummet.

"Between 2000 and roughly 2008, the Somali community in Minnesota actually had some of the highest vaccination rates for 2-year-olds of any population in the state," said Michael Osterholm, regents professor and director of the Center for Infectious Disease Research and Policy at the University of Minnesota and a former state epidemiologist for Minnesota.

As parents searched for answers as to why some Somali children were diagnosed with autism, they landed upon the work of discredited British researcher Andrew Wakefield , who first proposed a link between vaccines and autism in a paper later found to be fraudulent, Osterholm said.

At the same time, local anti-vaccination activists started to hold meetings in the community, he said.

"So, by about 2008, we started to see the vaccine rates drop as the word got through the Somali community that autism was linked to measles vaccination," he said. "In the years since then, Andrew Wakefield has actually been brought in several times to the Somali community here in Minnesota to actually give presentations supporting this information. ... His work has been retracted."

Three years later, a University of Minnesota research project investigated whether there was a higher prevalence of autism in Somali children who live in Minneapolis versus non-Somali children in Minneapolis. The project included data on children who were 7 to 9 years old in 2010.

The researchers found Somali and white children in Minneapolis to be equally likely to be identified with autism , and both groups were more likely to be identified with autism than non-Somali black and Hispanic children.

Meanwhile, a precipitous dropoff in vaccination coverage still continued among children of Somali descent, Ehresmann said.

Osterholm said that a measles outbreak hit the Somali community in Minnesota in 2011. Though it was smaller than the current outbreak, it was largely associated with children not being vaccinated, he said.

"Measles finds unvaccinated people, and this outbreak has two key points," Ehresmann said. "One is the effect of targeted misinformation on a vulnerable community, but the other is that if you're not vaccinated, you are vulnerable."

Fighting an outbreak

Health officials in Minnesota offered MMR vaccination recommendations last week in response to the recent outbreak of the measles virus. The vaccine is typically given to children in two doses: at 12 months and then at 4 to 6 years old.

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However, for children who have had one dose of the MMR vaccine and live in counties where measles cases have been identified, officials recommend that they get their second dose as soon as possible if their first was received at least 28 days ago.

All Somali Minnesotan children who received their first dose at least 28 days ago should do the same, according to officials. Additionally, health care providers statewide may recommend an early second dose during routine appointments for children.

Health officials recommended that all children 12 months and older who have not received a MMR vaccine should receive a first dose as soon as possible. It was also recommended that adults born in 1957 or later, who have not received a vaccine and have never had measles, should do the same.

As health officials continue to investigate where measles exposure may occur and who might have been exposed, guidelines have been released for health care professionals to help minimize measles transmission in Minnesota.

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"Measles is a serious disease. You can have pneumonia and dehydration ... and people do die from measles, so we take it very seriously," Ehresmann said.

"Our goal for measles control is to protect all the individuals in the state, but for some people, they can't be vaccinated because of health conditions ," she said. "There is some level of concern about those individuals, and if this outbreak keeps spreading, that just increases the likelihood that there may be individuals who are in high risk or have high-risk conditions that will be affected."

Osterholm compared the outbreak to a forest fire.

"Measles is by far one of the most infectious of all the infectious disease agents we deal with," he said. "If you get a major outbreak started in a community, like the Somali-Americans, the sparks fly out of that fire and then start forest fires around the state, and that's what we're concerned about today."

The Centers for Disease Control and Prevention says measles "is so contagious that if one person has it, 90% of the people close to that person who are not immune will also become infected."

It happened in Disneyland and at a megachurch

Although measles is still common in many parts of the world -- including countries in Europe, Asia and Africa -- the disease was eliminated in the US in 2000, according to the CDC

"So the cases that we see are cases that are imported or brought in from other countries, at this point," Ehresmann said. "You just don't know when it's going to happen."

In recent years, cases in the United States have quickly spread among those who have not been vaccinated.

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"We shouldn't be spending hundreds of thousands of public health dollars to battle an outbreak that doesn't need to be," Ehresmann said. "We collectively can prevent these things from happening by vaccinating."