For the past two weeks, wildfires have reduced the number of Oregonians who received COVID-19 tests. One result: a higher percentage of tests coming back positive.

For the week beginning Sept. 13, 6.2% of tests came back positive, according to initial data. The previous week, it was 5.4%.

The likely upshot? An even longer wait for school classrooms to reopen.

Gov. Kate Brown has set a benchmark—less than 5% positivity on tests statewide for three consecutive weeks—as the target required for reopening schools.

But wildfires made getting a COVID-19 test more difficult: Drive-thru testing sites closed amid smoke, for example. That meant that people who still sought testing were more likely to be sick, so the positivity rate increased.

Fewer tests, with a higher positivity rate, hint that health officials have even less of an idea of where the disease is spreading.

As a result of the wildfires, many Oregonians stayed home to avoid the smoke, which could reduce the spread of COVID-19. But at the same time, the state saw thousands of evacuations, including at state prisons, which could result in increased spread as people were sent from one location to another.