With the omicron variant now detected in 39 states in the US, federal mask mandates have been extended until March 18 in an effort to curb the spread, President Joe Biden recently announced. The federal mandate was originally supposed to expire on Jan. 18.

The federal requirement to wear a mask over the nose and mouth applies to people riding the bus, train and airplanes The extension is driven by a concern that the country could soon be fighting two COVID-19 variants at once. The highly contagious delta variant is still circling the country, while the new omicron variant has cases rising rapidly.

Last week, a statewide mask mandate for California was reinstated for indoor public places — effective Wednesday — and will last at least a month. California joins seven other states (Hawaii, Illinois, Nevada, New Mexico, New York, Oregon and Washington) and Puerto Rico in requiring most people to wear masks indoors regardless of vaccination status. Connecticut’s indoor mask mandate only applies to the unvaccinated.

The World Health Organization and the US Centers for Disease Control and Prevention continue to recommend everyone wear a face mask in crowded areas, regardless of vaccination status. While scientists are testing the effects of omicron on existing vaccines, it’s possible for people with breakthrough infections to spread any COVID-19 variant. Although the CDC believes vaccinated people may be contagious for shorter periods of time, they can and do contribute to new cases, especially for people who are asymptomatic and may not be aware they’re infected.

Both the WHO and CDC agree that people who aren’t vaccinated should continue to wear face masks because they account for the majority of COVID-19 cases and deaths around the world. As omicron spans the globe, scientists agree that anyone eligible for a booster shot should get one (here’s how to quickly make an appointment). We continue to update this story as new information comes to light.

Here’s the latest on mask mandates and tighter restrictions

The Biden administration extended its mask mandates for those traveling by trains, buses and airplanes on Dec. 2 due to concerns around the new omicron variant. And while the US has travel bans to prevent the new variant from spreading, omicron has already made its way into at least 39 states.

Other countries have also begun tightening COVID-19 restrictions. For instance, Germany recently announced a lockdown for those who are unvaccinated. Some states in the US have also tightened restrictions, requiring proof of full vaccination to enter businesses.

Which states have mask mandates?

The following states require most people to wear masks while in an indoor public setting.

• California
• Hawaii
• Illinois
• Nevada
• New Mexico
• New York
• Oregon
• Washington

The territory of Puerto Rico also requires masks for everyone indoors, while Connecticut requires masks indoors only for unvaccinated people.

Why are coronavirus variants like omicron and delta serious?

A new study shows omicron is four times more transmissible than the delta variant, which was considered the most contagious of the variants identified so far, according to the WHO, but omicron tests are still underway and guidance could change. It’s too early to tell how dangerous the omicron variant is at this time, though symptoms so far appear mild. It is understood to have more mutations than the delta variant.

Both variants are spreading among both the vaccinated and unvaccinated population, though hospitalizations, serious illness and death are less likely to occur in those who are fully vaccinated. Dr. Rochelle P. Walensky, director of the CDC, on Friday said nearly 80% of the confirmed omicron cases in the US are fully vaccinated, with about a third also having received a booster.

CDC guidance: Fully vaccinated should continue wearing masks in some areas

The current CDC guidance for mask wearing says that everyone age 2 years and older, vaccinated and unvaccinated, should continue wearing masks indoors when in public places, especially if in a high COVID-19 transmission area, to help prevent spreading the disease to others.

Earlier this year, the guidelines said those who are fully vaccinated can «resume activities without wearing masks or physically distancing» except where required, such as in planes and businesses. But that guidance quickly changed over the summer when it was found the delta variant can cause breakthrough infections in vaccinated people.

What is the WHO’s position on mask wearing?

Wearing a mask consistently continues to be important, even for people who are vaccinated, a WHO official said during a press briefing. «People cannot feel safe just because they had the two doses. They still need to protect themselves.»

Wearing masks in public places is essential to keep people from inhaling particles that will cause them to become sick, Dr. Maria Van Kerkhove, an American infectious disease epidemiologist, said during the same briefing.

While the Pfizer and Moderna vaccines are showing robust protection against variants, breakthrough infections can still occur.

For more information, here’s what you need to know about «long COVID» and how it’s treated. Also, read up on these COVID-19 vaccine side effects and important dos and don’ts of getting your COVID-19 vaccine.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.