On Friday, the Pennsylvania Department of Health added Missouri and Wyoming.
These states join Alabama, Arizona, Arkansas, California, Florida, Georgia, Idaho, Iowa, Kansas, Louisiana, Mississippi, Nevada, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Utah, which remain on the advisory list.
Health officials said if you have traveled, or plan to travel, to an area where there are high amounts of COVID-19 cases, it is recommended that you stay at home for 14 days upon return to Pennsylvania.
If you travel to any of the states on the list, it is recommended that you quarantine for 14 days upon return.
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Cases in Pennsylvania
In July, Pennsylvania's 14-day rate of new cases per 100,000 residents has risen by more than 50%, from below 60 to 90.
The seven-day positivity rate - based on the Health Department's daily public disclosures of the number of people who are newly confirmed to be positive and the number of people who tested negative - has gradually increased in July, from about 4.5% to 5.8%.
Deaths have declined from June to July, although hospitalizations are on the rise in July, according to state data.
The Department of Health reported more than 960 additional confirmed virus cases Thursday and 16 new deaths. The virus has infected more than 104,000 people in Pennsylvania since the beginning of the pandemic. More than 7,000 have died, most of them in nursing homes.
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Health Secretary Rachel Levine said the data available to the Department of Health shows that the virus is spreading primarily to people in their 20s, 30s and 40s who are getting together in bars, restaurants and nightclubs. It is a trend, she said, being seen throughout the country and backed up by the White House's observations.
Health officials in Philadelphia and Allegheny County have independently cited contact tracing information in line with that trend, as well.
Levine also warned of rising case counts in states along the East Coast.
"There are obviously significant outbreaks in Florida, in Arizona, in Texas, California now and other states, but we are seeing that come up the eastern seaboard," Levine said. "There are increases in Georgia, the Carolinas, Virginia and Maryland, and so we're not immune to the spread of this virus."
The Associated Press contributed to this report.