Will outdoor transmission of the contagious delta variant change mask guidelines?
mikimad/E+/Getty Images

A Guide To Outdoor Transmission & The Delta Variant

Because we all want to know if masks need to be worn outside again.

Just when it seemed like things were getting back to baseline, the pandemic has pitched yet another curveball. Thanks to the highly transmissible Delta variant of Covid-19, CDC mask guidelines have changed again, and people have questions about delta and outdoor transmission. Like, is wearing a mask outdoors necessary again? And just how contagious is this strain of COVID-19? Read on to see what is known now and what the experts have to say.

What Is The Delta Variant?

First detected in the U.S. back in March 2021, the Delta variant is currently the dominant strain of Covid in the United States. According to the Centers for Disease Control and Infection (CDC) information page on Covid-19 variants, “These variants seem to spread more easily and quickly than other variants, which may lead to more cases of Covid-19. An increase in the number of cases will put more strain on healthcare resources, lead to more hospitalizations, and potentially more deaths.”

Is Delta More Contagious Than Other Covid Strains?

Pediatric hospitalist at The Herman and Walter Samuelson Children's Hospital at Sinai, Dr. Talia Levy, tells Romper that the Delta variant “is believed to be the most contagious strain of Covid-19 we have seen so far.” As Romper previously reported, “The Delta variant appears to be about twice as contagious as the original strain of Covid.”

Dr. Vincent Hsu, MD, MPH, Executive Director of Infection Control and Hospital Epidemiologist at AdventHealth tells Romper that the virus’ mutation between strains is what makes Delta so transmissible. “Due to its mutations, many more virus particles are generated when the Delta variant infects a person, thus making it easier to infect someone else,” Hsu says. “It is this infectious property that allowed it to now become the dominant strain in the United States.”

As a new strain, experts are still uncertain of whether this variant is likely to cause more severe illness in those who are infected.

“There have been conflicting data whether Delta variant causes more severe disease. This is a new strain to the United States, and hopefully soon we will learn more about this,” Hsu says. “However, we do know that individuals who have been fully vaccinated against Covid-19 are greatly protected against severe disease and hospitalization compared to those who are unvaccinated. Thus, for adults and children age 12 and older, the best way to protect yourself against getting serious illness is to get vaccinated.”

Krit of Studio OMG/Moment/Getty Images

Is Delta More Transmissible Outdoors Than Other Variants?

“Current data suggest the risk of transmission of SARS-CoV-2 in outdoor settings is minimal,” the CDC website states. But, if Delta is spreading more easily than other variants, does that mean that it will spread outdoors as well?

“While outdoor environments do lower the risk of viral spread, the Delta variant is more transmissible across the board — making it more transmissible in both indoor and outdoor settings,” Levy tells Romper.

Hsu’s take on outdoor spread varies slightly. “What we have learned about Covid-19 is that this virus is not easily transmitted outdoors due to the very quick dilutional effect and air currents,” Hsu tells Romper. “While the Delta variant does result in more virus particles being transmitted, it appears unlikely to make a difference compared to previous strains, although we do not have scientific studies yet to confirm this.”

When Should Masks Be Worn Outdoors?

The CDC now recommends that even fully vaccinated individuals should wear masks in public indoor settings in areas where high transmission of the delta variant is present. The CDC also now recommends full masking in public schools for every child and adult, regardless of vaccination status. They also maintain their recommendation that everyone aged 2 and older wear a mask in indoor public spaces if unvaccinated.

Despite an array of updated guidance in light of the Delta variant, the CDC has not changed their recommendations for outdoor masking yet. To date, the CDC maintains, “In general, you do not need to wear a mask in outdoor settings.” They do, however, suggest that individuals consider wearing a mask in crowded outdoor spaces where transmission rates are high or if immunocompromised.

“The length of time and the close proximity spent with an infected individual are the two most important factors that would affect the risk of transmission anywhere,” Hsu says. “Outdoors, you would not need a mask if you walk close by someone that might be infected or spend time together at a playground where there is sufficient distance from others. Outdoors, you would want to consider wearing masks when sitting next to a person for a prolonged period of time, such as 10 to 15 minutes.”

A person’s vaccine status should also be taken into consideration, according to Levy. “For outdoor activities among fully vaccinated individuals, masking is generally not necessary, so taking a walk or going out to a park should be fine,” Levy says. “However, you may want to consider masking when attending crowded outdoor events or if you are living with someone who is immunocompromised.”

But what about our kids who aren’t able to be vaccinated yet?

“Even for unvaccinated individuals, some outdoor activities do not need a mask,” Levy tells Romper. “However, for those living in areas with high rates of Covid transmission, masks should be worn if you are going to be within six feet of other unvaccinated individuals. For instance, if children will be playing closely together on a playground, they should wear a mask, but if you are walking around the neighborhood with other members of your household, a mask is not necessary.”


Dr. Vincent Hsu, MD, MPH, Executive Director of Infection Control and Hospital Epidemiologist at AdventHealth

Dr. Talia Levy, Pediatric Hospitalist, The Herman and Walter Samuelson Children's Hospital at Sinai