The U.S. Centers for Disease Control has sent two epidemiologists to Washington State.
The investigators will try to find out what's causing the state's rapid rise of whooping cough cases.
The investigators are in Washington to help the state figure out how the number of whooping cough cases has reached epidemic levels. They're here at the request of Washington Secretary of Health Mary Selecky, and U.S. Sen. Maria Cantwell.
To date there are more than 1,100 reported cases of whooping cough in Washington -- mostly adults. That's ten times higher than they were the same time last year.
Whooping cough is a highly contagious respiratory tract infection. It can be fatal to infants. So far this year, 20 babies have been hospitalized.
Health officials are urging adults and teens to get vaccinated. They could be contagious without knowing it, and could infect other adults or children.
Also this week, more than 27,000 doses of the pertussis vaccines will be available to adults without insurance.
This story originally appeared on Oregon Public Broadcasting.