AUDIE CORNISH, HOST:
An unusually large outbreak of measles is raising alarm across the Pacific Northwest. Officials in Washington state have even declared a public health emergency, as NPR's Patti Neighmond reports.
PATTI NEIGHMOND, BYLINE: So far, 35 cases of measles have been confirmed in Washington state alone, mostly among children under 10. Washington state epidemiologist Dr. Scott Lindquist says this is likely only the beginning, since many of the families with sick kids traveled to very public places.
SCOTT LINDQUIST: Like Costco or Ikea or the airport or a professional basketball game.
NEIGHMOND: And because the telltale measles rash may not appear for four days into the illness, people may not know they're infected and could easily, unwittingly expose others to this extremely contagious virus.
LINDQUIST: And our big concern is for folks that are immunocompromised, pregnant women, young kids or those that are unvaccinated could be at risk for this disease.
NEIGHMOND: Infants can't be vaccinated until they're 1 year old. Pediatrician Peter Hotez with Baylor College of Medicine's National School of Tropical Medicine says people often forget or just don't even know how severe measles can be.
PETER HOTEZ: Before widespread vaccination, measles was the single leading killer of children in the world. And to this day, it still kills 100,000 kids. It causes measles pneumonia, measles encephalitis, deafness. Measles is a bad actor.
NEIGHMOND: Most of the children infected with measles in Washington state were not vaccinated against the disease. Hotez.
HOTEZ: In the Pacific Northwest, you have a very aggressive anti-vaccine lobby, with websites - by some estimates, up to 480 misinformation websites, all amplified on social media.
NEIGHMOND: Like Washington and Oregon, about half of all states in the U.S. allow parents to opt out of vaccinating their children if they have a personal or philosophical objection.
Washington state officials are now beginning the arduous and costly task of tracking down everyone who might've been exposed to the virus and cautioning them to be on the alert for symptoms, including runny nose, red eyes, fever and the rash. If they believe they're infected, Dr. Lindquist says, they should contact their health care provider and isolate themselves at home, so they don't expose others.
Patti Neighmond, NPR News.