(CNN)With Covid-19 tests hard to find in many parts of the country and the Omicron variant spreading rapidly, health experts are advising those with symptoms to isolate themselves if they even only suspect they have the virus.
And with the recent news that rapid antigen tests may lag in detecting positive cases when compared to PCR tests, the best time to take a rapid test may be a day or two after symptoms arrive, epidemiologist Dr. Michael Mina said Thursday.
"The important thing is, when you feel symptoms, assume you're positive at this point, especially with Omicron being so prevalent," Mina said in an interview with telehealth company eMed, where he is chief medical officer.
For those who take a rapid test and show a positive result after swabbing, yet the line shown is very faint, they may have an active infection and still be contagious, he said.
"Does it mean you're going to walk into a room and be a superspreader? No. But does it mean that you should go to your 90-year-old grandmother and hug her? I would say no, I wouldn't do that. I would not want to personally be sitting next to somebody who's still positive in any way on these tests," Mina said.
Health officials in Louisiana echoed the message Thursday as the state reported a record daily number of infections.
"When you're in a surge like we are right now and Covid is everywhere -- and it is everywhere right now -- if you have trouble getting a test, a take-home test particularly, and you do have symptoms, the prudent thing to do is just assume you have Covid and isolate away from other people. That's the safest thing to do right now," state health officer and medical director Dr. Joseph Kanter said.
Leaders in multiple states are working to expand access to testing as a surge in demand paired with a lack of supply has led to numerous shortages.
In Minnesota, officials said a new testing site would be opened and that 1.8 million rapid tests would be sent to schools. In Maryland, 20 additional testing locations will be set up outside hospitals to divert people from going to emergency rooms for Covid-19 tests.
Yet the buildup of testing has not been as smooth in every state. As many as 1 million unused rapid test kits expired in a Florida warehouse, a top state official said on Thursday.
The stockpile sat idle during the fall when cases fell in Florida and demand was low, Florida Department of Emergency Management Director Kevin Guthrie said, and the kits expired "before December 26 to December 30."
The issue with testing is been just one part of the response to the pandemic that needs to be retooled in the face of a "new normal" of living with the virus, six former advisers to President Joe Biden wrote in the medical journal JAMA Thursday.
The authors described the initial response to the virus as "seriously flawed," and called for low-cost and accessible testing with immediate advice when someone receives positive results. Other suggestions include modernizing data and public health infrastructure as well as vaccine mandates and accelerated efforts to develop a universal coronavirus vaccine.
Vaccinations remain critical to fight pandemic, officials say
The National Guards in Ohio, New Hampshire and New Jersey announced plans to deploy members to assist hospitals and long-term care facilities that face shortages of workers, who face higher chances of exposure due to an influx of patients and must isolate after testing positive.
Widespread infections are also stretching other industries such as public safety departments. In Los Angeles, 505 police officers and 299 fire department employees are in quarantine at home as of Wednesday.
"These are big numbers, numbers that are reflecting the staffing challenges that we all face," said Mayor Eric Garcetti.
"Our continued response time will see some delay in routine calls," LAPD Chief Michel Moore said, but stressed that 911 services are fully staffed.
Health experts are reminding that being vaccinated gives those infected the best opportunity to recover quicker and avoid severe illness. Reports demonstrate that those unvaccinated remain at higher risk.
In Maryland, "75% of the patients who are currently admitted in our hospitals with Covid-19 across the medical system are unvaccinated," according to Dr. Mohan Suntha, president and CEO of the University of Maryland Medical System, and less than 5% of all patients who are hospitalized with Covid-19 are vaccinated and boosted.
Connecticut Gov. Ned Lamont said Thursday that all long-term care staff and contract employees in the state will be required to get a Covid-19 booster by February 11 if eligible.
In addition, hospital employees will be mandated to get the booster, Connecticut Hospital Association Vice Chairman Patrick Charmel said. Officials expect all staff who need a booster to have one by early March.
CDC updates prevention guidance in schools
Aligning with its latest quarantine and isolation recommendations, the US Centers for Disease Control and Prevention on Thursday updated guidance for Covid-19 prevention in K-12 schools.
Students, teachers and staff with Covid-19 should stay home and isolate away from others for at least five days, the guidance said. Day 0 is considered the first day of symptoms or the day of a positive viral test for people who do not have symptoms.
People whose symptoms are improving can leave isolation after five full days if they are fever-free for 24 hours, the CDC said. They should wear a mask around others for an additional five days.
Children who have been exposed to the coronavirus and have not been fully vaccinated should quarantine for at least five days after their last close contact with a person who has Covid-19, the guidance said. Adults who are not vaccinated against Covid-19 or who have not received a booster shot are also advised to follow this recommendation.
For the first time since July, the CDC will hold an independent telebriefing on the pandemic on Friday. The CDC usually participates in joint briefings with officials from the White House or the National Institutes of Health.
CNN's Virginia Langmaid, John Bonifield, Naomi Thomas, Jamie Gumbrecht, Chris Boyette, Carma Hassan, Stella Chan, Amy Simonson, Steve Contorno and Taylor Romine contributed to this report.