A mumps outbreak in King County that started late last year is still forcing some unvaccinated Auburn students to stay home as the new calendar year begins.

The Auburn School District says 143 students who were told to go home in early December (down from over 200 in November) were allowed to return last Wednesday when classes resumed from winter break.

But on Friday, 44 of those students were told to go home again because the 25-day exclusion window (from the most recently diagnosed cases at those schools) had not yet passed.

Some of those students will not be allowed back for a few days and some as late as Feb. 1. The district is taking this on a school-by-school basis. Here's the list of schools and return dates:

• Lake View Elementary: Jan. 12

• Gildo Rey Elementary: Jan. 12

• Cascade Middle School: Jan. 13

• Pioneer Elementary: Jan. 13

• Auburn Riverside High School: Jan. 17

• Olympic Middle School: Jan. 17

• Arthur Jacobsen Elementary: Jan. 23

• Mt. Baker Middle School: Jan. 27

• Terminal Park Elementary: Jan. 30

• Auburn High School: Feb. 1

As of late December, there was a total of 44 possible or confirmed cases of mumps across King County. Over 60% of the cases were in children age 17 and younger, and 59% were up-to-date on their MMR vaccination.

Mumps is caused by a virus. It can cause fever, headache, and swelling of the cheeks and jaw. Most people recover from the illness within a few weeks. It is spread through coughing, sneezing, spraying saliva, or touching surfaces shared with an infected person.

Mumps can be prevented by staying up-to-date on MMR vaccinations, washing hands frequently, and avoiding shared drinks and utensils. However, a spokesperson for King County Public Health said the vaccination is effective, but not perfect. Some of those with confirmed cases of the mumps were vaccinated.