Measles cases in the United States have passed 4,000 for the year. The Centers for Disease Control and Prevention reported 4,080 confirmed cases on Friday, as of October 8. That is the most since 1991, CIDRAP reported, and 78% more than all of last year, when the country had 2,289 cases.

The weekly rise was about 5%, down a bit from the week before, Contagion Live reported. It is the ninth straight week of big gains.

So far, 414 people have been hospitalized, or about 10% of cases. Children and teens up to age 19 make up 42% of the sick, and adults make up 40%, Reuters reported. About 95% of cases are in people who were not vaccinated or whose status is unknown.

Pennsylvania is the center of the outbreak. The state reports 1,136 cases this year, with 157 in the past week. Lancaster County has 415 of them. Pennsylvania has also linked five deaths to measles, two infants and three adults. The CDC still lists only two measles deaths nationwide, because it now uses federal death records instead of state reports, a change that has drawn questions.

Other states are busy too. New York declared a statewide emergency this week. Wisconsin, Ohio and Kentucky each have more than 100 cases.

Measles was declared wiped out in the United States in 2000. It has come back as vaccine rates slipped. Kindergarten coverage for the measles shot fell from 95.2% in 2019 to 92.4% last school year, the CDC says. Experts say about 95% is needed to stop spread. Two doses of the MMR shot are 97% effective.

The CDC has sent about $100 million to states in recent weeks to fight outbreaks, CIDRAP reported. Parents can check their children's shot records with their doctor or state health department.

What we know: Cases topped 4,000, and most patients were not vaccinated.
What we don't: How many deaths the CDC will count once its review ends.