The outbreak of measles in several states have health officials concerned. At least 70 cases have been reported so far this year, the highest total in six years.
It's the largest number of cases since 2001 when 116 cases were reported, according to CDC records.
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Officials expect this year's tally to keep climbing past that mark, said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases.
The Centers for Disease control and Prevention reports that most of the cases are due to outbreaks overseas. They are found mainly in children who have not been vaccinated for religious or other reasons or were too young.
Cases have declined steadily in the U.S. since the early 1960s when children received innoculations for the disease.
So far this year, the CDC has confirmed reports of 64 cases in nine states. There were no deaths, but 14 people were hospitalized, said CDC spokesman Curtis Allen.
Measles is caused by a virus that typically grows in cells that line the back of the throat and line the lungs. The infection is spread through contact with a sneezing, coughing, infected person.
Some mild symptoms include rash, high fever, cough, runny nose, and red, watery eyes. But in some cases the illness can be more severe with about 1 in 5 measles sufferers experiencing diarrhea, ear infections, pneumonia, encephalitis and even seizures and death.
Health officials say parents must get their children immunized.
"It's not acceptable to have any child improperly or incompletely vaccinated because that increases their risk of disease and also increases the risk of outbreaks in the community," said the CDC's Elizabeth Luman.
Health Officials: Vaccinate Your Children
Out of 64 cases reported to the CDC as of last week, 63 were unvaccinated or it wasn't known if they were vaccinated. At least 54 of the cases came from outbreaks in Switzerland, Israel or other countries, Allen said.
Children under a year old represented 13 of the cases in the U.S. Doctors recommend that children do not get their first measles shot until they're at least one-year-old. The reason is their immune systems are not mature enough to react to the vaccine.
Such children can easily pick up infections from those around them, said Dr. William Schaffner, chairman of Vanderbilt University's department of preventive medicine.
"We have a responsibility not only to ourselves but to everyone around us" to get recommended vaccinations, he said.
The largest concentration has been in New York City, with 22 cases. Arizona has had 15, California, 12, and Michigan and Wisconsin have each had four. Hawaii, Illinois, Pennsylvania, Virginia and upstate New York also reported cases.
Fifty years ago was the worst measles outbreak in recorded history. More than 763,000 cases were reported, including more than 550 deaths.
Source: The Associated Press