With a "tripledemic" of Covid-19, influenza, and respiratory syncytial virus (RSV) driving spikes in infection and hospitalization rates, health officials are encouraging individuals "to wear a high-quality, well-fitting mask to prevent the spread of respiratory illnesses."

Cases are spiking amid a 'tripledemic'

Over the past two weeks, Covid-19 infection and hospitalization rates have increased by 56% and 24%, respectively. In addition, CDC estimates that there have been about 13 million illnesses and 7,300 deaths from influenza this season. Although RSV rates seem to be declining, infection rates remain high in many areas.

According to William Schaffner, a professor of preventive medicine at the Vanderbilt University School of Medicine, rates of Covid-19, influenza, and RSV "may be more intense or a little bit less intense in some parts of the country, but really, the entire country is being affected."

In California, Covid-19 transmission rates have increased significantly in recent weeks. As infection rates increase, "your chance of catching COVID during your routine activities—grocery shopping, eating out, running errands, going to work—will increase," according to Los Angeles County Department of Public Health Director Barbara Ferrer.

For example, with a Covid-19 case rate of roughly 260 cases a week for every 100,000 Los Angeles County residents, there is an 80% to 90% chance that at least one person at an event with 200 people would be infected, according to Ferrer.

"If you're going to an event such as a concert or a large Christmas party, there is now a higher likelihood that one or more persons at the event is infected, they could unknowingly infect you, and you in turn could unknowingly infect your friends, your co-workers or your family," Ferrer said.

While Covid-19 may only result in a mild infection for many, certain populations have a higher chance of serious illness.

"For the millions of people in the higher-risk categories—our elderly family members and friends, those with underlying health conditions and those who are immunocompromised—increased chances of being exposed can have a devastating impact," Ferrer said.

Meanwhile, Los Angeles County's positivity rate for influenza is 30%--an increase from 25% the previous week.

With rising infection rates, several hospitals in Los Angeles County have reported intense strain over the demands of patients sick with Covid-19, influenza, or RSV.

According to a CNN analysis of HHS data, hospitals are currently fuller now than they have ever been during the pandemic. Over the past two weeks, the number of hospital beds in use nationwide has increased by eight percentage points to over 80%.

Health officials encourage masking to lower transmission

Most health officials agree that wearing a mask lowers the risk of viral transmission—a claim supported by a wide body of academic research.

Currently, CDC is advising wearing a mask on a county-by-county basis, depending on local Covid-19 infection rates. However, CDC Director Rochelle Walensky, last week, said, "You don't need to wait for CDC's recommendation … to wear a mask."

"We also encourage you to wear a high-quality, well-fitting mask to prevent the spread of respiratory illnesses," Walensky said. "CDC continues to recommend masking for anyone choosing to travel by plane, train, bus or other form of public transportation."

In addition, Schaffner said anyone living in a high-risk household should "put your mask back on" in public.

Separately, Helen Chu, an associate professor of allergy and infectious diseases at UW Medicine, said everyone should wear a mask while infection and hospitalization rates remain high. "I think it's a good time to mask," she said. "Given where we are right now with hospitals being at very close to capacity, especially in pediatric hospitals with R.S.V. and with flu, I think that anything that you can do to slow down community transmission is going to be helpful."

According to the California Department of Public Health, "[w]earing a mask in indoor public places, among other safety measures, effectively slows the spread of respiratory viruses that make children and the elderly very sick."

A large body of evidence suggests that masks can help to reduce the transmission of several respiratory viruses. For example, a paper published in 2020 showed that individuals infected with either Covid-19 or influenza expelled fewer viral particles when they wore a surgical mask. In another study of Covid-19 policies in Boston-area schools, researchers found that the elimination of the mask mandate in 2022 was associated with almost 12,000 additional cases among students and staff.

During the 2020 and 2021 winter seasons, transmission of influenza and other respiratory viruses was low—a pattern that was largely attributed to Covid-19 prevention measures. "What Covid has shown us, because we've been social distancing and mask wearing, is that influenza, the common cold viruses, RSV are suppressed remarkably" by these measures, Schaffner said.

"The basic truth is that masks work," said Syra Madad, senior director of the systemwide special pathogens program at New York City Health + Hospitals. "Whether you're talking about Covid-19 or other respiratory viruses like R.S.V. and flu, wearing a mask will help protect you against all these respiratory viral illnesses." (Lin II/Money, Los Angeles Times, 12/13 [subscription required]; Smith, New York Times, 12/13)