Centre County saw its largest single-day increase of COVID-19 cases Sunday, adding 43 cases for a total of 356 confirmed and probable cases, according to data from the state Department of Health.
The 14% increase comes as the state is taking steps to try to reverse the trend of increasing case numbers before the beginning of the school year.
State Department of Health spokesman Nate Wardle said in an email Wednesday that the department "has determined a number of the positive test results were not valid. We are reviewing those tests, retesting, and will change our data (as needed) to reflect the results of these tests in the near future."
In Centre County, the previous record for largest one-day increases was 11 cases on April 7 and again in June.
Mount Nittany Health's Chief Medical Officer Nirmal Joshi said in an email that they notified the state Department of Health after noticing "an unusual spike in the number of positive test results at the end of last week."
"We are collaborating with the DOH to investigate this sudden spike and to coordinate additional testing of these individuals," Joshi said. "We are expecting results to be returned in the next few days and we will continue to work closely with the Department of Health."
Mount Nittany Health and its medical center serve central Pennsylvania, including Centre County.
The Department of Health warns that it is seeing "significant increases" among younger people, particularly 19- to 24-year-olds. In Pennsylvania's northcentral region, which includes Centre County, 19- to 24-year-olds went from making up nearly 8% of cases in April to 13% of cases so far in July.
There are between one and four cases in the 16802 zip code, Penn State's University Park campus. The Department of Health does not provide the specific number of cases for a zip code when there are fewer than five.
Penn State Athletics confirmed last week that a student-athlete tested positive. The university has brought many athletes back to campus for training this summer, and Athletics has said those students would be tested on arrival and again if they left the area.
At the same time, the university has been getting ready for the return of students for on-campus classes this fall. But, many in the community are concerned about how much student behavior can be controlled off campus, including requiring mask-wearing and limiting off-campus parties.
In an email to the community Thursday, Penn State President Eric Barron said the university will have more details about its plans for bringing students back to campus at an upcoming town hall.
"We understand that the current lack of details on much of our important planning has caused stress for many on our campuses and in our communities," Barron said.
Overall, there are a total of 107,425 cases in Pennsylvania, an increase of 800 since Saturday.
"Preventing the spread of COVID-19 is essential to protecting the health of Pennsylvanians. We are continually monitoring increases in COVID-19 cases happening in Pennsylvania. Even small case increases are concerning and are being watched very carefully," Wardle said. "It is vital for Pennsylvania to remain vigilant in our battle against COVID-19. Wearing a mask, social distancing and washing your hands are simple things we must do every day to minimize risk."
This is a developing story and will be updated as more information becomes available.