By Talal Ansari and Allison Prang

Louisiana will remain in Phase 2 of its coronavirus reopening plan for an additional two weeks to assess the damage caused by Hurricane Laura, which is set to make landfall there on Thursday, Gov. John Bel Edwards said.

"We're basically going to be blind for this week because we'll have to discontinue much of our community-based testing," Mr. Edwards said at a Wednesday press conference. "The prudent thing is to go two more weeks and see where we are."

Phase 2 in Louisiana includes a statewide mask mandate, the closure of bars for on-site consumption and crowd limits of no more than 50 people.

Mr. Edwards said the state intends to use hotel and motel rooms to house those displaced by the storm to allow for social distancing and to mitigate dangers posed by the spread of the virus.

"We really don't want people using congregate shelters unless it is an absolute last resort," the Democratic governor said. "And by the way, when we use them, we're going to make them as safe as they can be," he said, adding that emergency lodging would be used outside of state lines as well.

Mr. Edwards also said the state hopes to restart Covid-19 testing, and the National Guard will help run numerous testing sites across the state.

To date, Louisiana has recorded 144,116 cases and 4,797 deaths since the pandemic began. The seven-day moving average for daily positive cases is down from last week, currently at 4.8%.

Hurricane Laura threatened both Texas and Louisiana as it gathered strength in the Gulf of Mexico on Tuesday. Officials in the states issued mandatory evacuation orders in a dozen coastal cities and counties, and voluntary evacuation orders in numerous others.

Shelters in Austin, Texas, hit capacity early Wednesday morning, the city said in a press release. In response, the city told residents to arrive at the Circuit of the Americas racetrack to await further accommodations. "Those seeking shelter from this weather event are welcome to wait at COTA to see when more hotel rooms become available," the city said.

In Texas, coronavirus cases have exceeded 600,000, and nearly 12,000 have died due to the virus. While new daily cases are down slightly, the positivity rate in the state remains high, with a 16.7% positivity rate for the seven-day average, according to Johns Hopkins University data.

The threat to the area comes as new coronavirus infections rose slightly in the U.S. for the second day but remained lower than in recent weeks.

The country reported about 38,200 new cases on Tuesday, according to data compiled by Johns Hopkins University, up a few hundred from Monday but still an improvement from last week, when cases topped 40,000 most days and neared 50,000 on some.

In all, 5.78 million people in the U.S. have been infected, nearly a quarter of the global total, according to the Johns Hopkins data. There have been more than 178,000 deaths in the U.S. and more than 820,000 world-wide.

The seven-day average of new cases in the U.S. for Aug. 25 was about 42,185 new cases, the lowest it has been since June 30, and lower than the country's two-week average of over 45,464 new cases, according to a Wall Street Journal analysis of Johns Hopkins data. When the seven-day average is lower than the two-week average -- which has been the case in the U.S. since July 26 -- it suggests cases are declining.

In Illinois, health officials and business leaders in rural parts of the state are raising alarms about rising infection rates that are fueling a steady increase in coronavirus cases statewide.

The state is one of 22 across the U.S. with a seven-day average of new cases that is higher than its 14-day new average. In six of those states, however, the difference is in the single digits. In Illinois, the difference between the seven-day average and 14-day average is about 92 cases.

New York City Mayor Bill de Blasio said that sheriffs have done 3,000 vehicle stops to work on enforcing rules for people coming into the city from certain states heavily affected by the virus. There have been two citations.

"If someone won't comply, then they're ready to provide the penalties," Mr. de Blasio said Wednesday. He said about one-fifth of the cases in the city are related to travel.

Mr. de Blasio also acknowledged that with schools reopening next month, there will likely be mixed results with some schools avoiding outbreaks, while others report new cases. "We'll have challenges undoubtedly but I think we see a lot of good examples from around the world of those challenges being managed well," he said.

Gov. Phil Murphy of New Jersey said the once-hard-hit state will allow gyms to open at 25% capacity. The new rules, which go into effect on September 1, still require attendees to wear masks and equipment to be placed at least 6 feet apart.

North Carolina State University said Wednesday it would send most of the roughly 6,200 students who live in campus housing back home, beginning Thursday, as case counts there continued to tick up and more clusters have been identified. Chancellor Randy Woodson said the increasing rate of positive cases and continued spread of the virus both on and off campus "have made our current situation untenable."

The school, which began classes Aug. 10, had already shifted to fully online instruction Monday. Students in off-campus housing may stay there but are expected to adhere to state regulations limiting group gatherings, the school said.

NC State had 277 people test positive in the past week, with a positive test rate of 13.8%. The positivity rate is 34% for student patients in campus health services and over 9% for those tested through surveillance programs, which is generally for asymptomatic individuals.

The California state Senate suspended its proceedings Wednesday after an individual who works there tested positive for Covid-19.

In a statement sent to staff, Senate President pro tempore Toni Atkins said only that the infected person is a "member of the Senate family" who was present in the state Capitol this week. Contact tracing has begun to alert potentially infected individuals.

According to a person who works inside the Capitol, Senate chambers are currently being deep cleaned. The state Assembly, which shares the Capitol building, continued its operations as usual.

The shutdown comes during the busiest time of the year for the California legislature, as it rushes to pass bills before the end of its two-year session on Monday.

California Gov. Gavin Newsom said that the state signed a contract with a diagnostic company that would allow it to process 150,000 more Covid-19 tests a day, with a one- to two-day turnaround. The additional capacity is expected to begin on November 1 and become fully functional by March 1.

Separately, in a paper posted online Tuesday, researchers who conducted a genetic analysis found that an international meeting of Biogen Inc. managers in February was a "superspreader event," in which clusters of infections are created through rapid transmission.

The conference likely helped spread the coronavirus from Boston to thousands of people as far away as Michigan, Virginia and Australia, the researchers said in the findings posted in a database for early versions of scientific papers. It hasn't been published in a peer-reviewed journal.

"Any infection that happens early on in an outbreak like this, where it's exponential, it's either going to peter out very quickly or wind up infecting a lot of people very quickly," said Stephen Schaffner, a study co-author and computational biologist at the Broad Institute of Harvard and MIT.

Write to Talal Ansari at Talal.Ansari@wsj.com and Allison Prang at allison.prang@wsj.com