(CNN)Health experts have long argued that face masks are critical to slowing the spread of the coronavirus and ending the pandemic. But some elected officials and their constituents still refuse to wear them.
Why you should wear a face mask even if your state doesn't require it
Last week, President Joe Biden criticized states, including Texas and Mississippi, for lifting Covid-19 restrictions, including mask mandates. He accused governors in those states of "Neanderthal thinking."
At least fifteen states -- representing 30% of the country -- don't require face masks.
With more than 500,000 Americans dead and new emerging variants of the virus, health experts warn that such policies could prolong the pandemic and result in more lives lost.
"We are not out of the woods. We haven't reached the end of the pandemic," said CNN medical analyst Dr. Leana Wen. "It's counterproductive and truly infuriating these governors are treating this as if the pandemic is over. It's not true."
"We could be at the precipice of a fourth surge, and we have a way to prevent it and that's keeping up our precautions for a while longer," she said.
Here are five reasons why experts say you should wear a face mask, even if your state doesn't require it:
The science is clear: Wearing face masks saves lives.
Numerous studies have shown that masks are the single most effective way to protect yourself and others from contracting the coronavirus, which causes Covid-19.
In counties that require masks, Covid-19 case and death rates slow down, according to the US Centers for Disease Control and Prevention (CDC).
Mask mandates were associated with a 0.7 percentage point decrease in daily rates of Covid-19 deaths up to 20 days after implementation and decreases of up to 1.9 percentage points up to 100 days later, according to new research published Friday by the CDC.
"Masks are a two-way street. Masks protect you and me" by preventing the spread of droplets and aerosol that may contain the virus, the CDC says in its mask guidance.
Dr. Anthony Fauci, the nation's top infectious disease expert, has even started wearing two masks.
"There are many people who take the commonsense approach," he told CNN. "If you're talking about a physical barrier -- and as the CDC recommends you want at least two layers within the mask as a physical barrier -- and you feel maybe more of a physical barrier would be better, there's nothing wrong with people wearing two masks. I often, myself, wear two masks."
The CDC last week released new data suggesting that double masking can significantly improve protection.
Layering a cloth mask over a medical procedural mask, such as a disposable blue surgical mask, can block 92.5% of potentially infectious particles from escaping by creating a tighter fit and eliminating leakage, researchers said.
The United States has made a lot of progress in the fight against Covid-19, including the development of safety protocols, enhanced treatment plans and vaccines.
The rates of infections, hospitalizations and deaths have decreased in many states since January, and nearly 90 million doses of vaccines have already been administered.
But abandoning face masks now could reverse those gains, health experts warn.
With tens of thousands of Americans still being infected daily, and more transmissible variants discovered, it's more important than ever to wear face masks and follow other safety guidelines.
"Please hear me clearly: At this level of cases with variants spreading, we stand to completely lose the hard-earned ground we have gained," said Dr. Rochelle Walensky, director of the CDC.
"I am really worried about reports that more states are rolling back the exact public health measures we have recommended to protect people from Covid-19," she said. "Please stay strong in your conviction. Continue wearing your well-fitting mask and taking the other public health prevention actions that we know work."