Americans worried about their exposure to coronavirus can check their symptoms with two new screening tools online.

The U.S. Centers for Disease Control and Prevention (CDC) added a “Coronavirus Self-Checker” to its website Thursday, and separately Emory University and Atlanta-based Vital Software Inc are launching C19check.com on Friday.

Oscar Health, a private health insurance company with a focus on technology, launched a similar assessment tool last week on its website that is open to non-members and members.

The sites are designed to enable people to assess the severity of their symptoms and help prevent emergency rooms and hospitals from being overwhelmed by patients who may not need immediate care.

Public health experts are urging the “worried well” and people with mild symptoms to stay home so doctors, nurses and other health workers don’t exhaust their limited supplies of masks, gowns and other protective gear as the number of coronavirus cases in the United States quickly grows.

“We know if everyone rushes to the ER or their physician’s office to get answers to their questions it won’t work,” Dr. Alexander Isakov, a professor of emergency medicine and executive director of Emory University’s Office of Critical Event Preparedness and Response, told Reuters.

“We think our tool can help communities and health systems get through what could be a really difficult time.”

CDC spokeswoman Kristen Nordlund said the agency worked with Microsoft to develop its self-checker system. She said it can assist people in pursuing “an appropriate level of care” and may help to reduce the burden on the healthcare system.

Both sites are similar in nature to work Isakov and others at Emory did on a self-triage tool for the H1N1 influenza outbreak in 2009 that both the CDC and Microsoft promoted at the time. The new tools offer an alternative to a screening site launched by Google’s sister company Verily that U.S. President Donald Trump began touting last week.

The Verily site also launched a lab testing center in two California counties around San Francisco earlier this week.

Oscar’s site also includes a testing center locator for the markets in parts of the 15 states where it offers health insurance plans, including New York. Oscar Chief Executive Mario Schlosser said that the company was working to broaden it out beyond those areas as more testing sites are available around the country.

Aaron Patzer, chief executive of Vital Software, said the company plans to make its COVID-19 checker available in other languages to assist more people around the world. More than 245,000 infections have been reported worldwide, including nearly 14,000 cases and at least 200 deaths in the United States as of Thursday.

On the new screening tools, people answer a series of questions about their age, symptoms and underlying medical conditions. Based on those responses, the systems assess the person’s risk of having coronavirus and advise whether they should self isolate at home or immediately seek medical attention.

Some medical providers warn that these online tools may misclassify some severely ill patients and cause them to delay getting care.

“You could get a false reassurance because what you put in would indicate you’re OK and you may not be,” said Deborah Burger, a registered nurse in California and president of National Nurses United, a union representing about 150,000 nurses across the country.

Isakov said the Emory-backed site doesn’t offer a diagnosis and always advises people to consult with their physician. “There is no replacement for the doctor-patient relationship. But these are extenuating circumstances in a pandemic,” he said.