UCHealth: Preventing “Superspreader” Events Fall & Winter

01 Oct UCHealth: Preventing “Superspreader” Events Fall & Winter

We curated this excellent article by Katie Kerwin McCrimmon from UCHealth Today. This must-read is titled “How you can prevent ‘superspreader’ events this fall and winter.”  Keep reading to the end to find out how to stay safe. Also read this related “To Your Health” post by Dr. Alan Safdi on social distancing.

Superspreader events — where a person with COVID-19 inadvertently infects multiple other people at the same time and place — are likely to increase as we head into fall and winter.

But, you can prevent superspreader events if you follow these relatively simple guidelines from Dr. Daniel Pastula, a UCHealth neuro-infectious disease expert and a neurohospitalist at UCHealth University of Colorado Hospital:

• Stay home when you are sick.
• Wear masks as much as possible.
• Avoid crowds and limit the number of people at events.
• Stay at least six feet away from people.
• Maximize “clean” air by holding events outdoors or with good ventilation indoors.
• Wash hands and frequently touched surfaces as often as possible.

“The risks of transmission aren’t the same across all events. There are some events or circumstances that are very risky for widespread COVID transmission. These are what we call superspreader events and they are largely preventable,” said Pastula, who is also an associate professor of neurology, infectious diseases and epidemiology for the University of Colorado School of Medicine and the Colorado School of Public Health.

Dr.-Dan Pastula of UCHealth.

Over the course of the pandemic, researchers have learned that the virus that causes COVID-19, SARS-CoV-2, likely spreads both through respiratory droplets and possibly via short-range airborne aerosols. These infectious particles can be very dangerous in poorly ventilated, crowded indoor environments and can lead to superspreader events.

Pastula doesn’t want to single out specific types of businesses or events, but people should be very careful if they work or spend concentrated time in crowded indoor environments.

Concerns about airborne aerosols prompted health experts at the Colorado Department of Public Health and Environment to issue new guidance in recent days about how to properly ventilate indoor areas as well as how employers can prevent outbreaks in workplaces.

A new understanding of how the virus spreads

While health experts and government officials are worried that coronavirus cases are going to spike throughout the fall and winter, Pastula said he’s actually quite hopeful because experts now have a much better understanding of how the virus spreads.

“Since we have a much better handle on how and why superspreader events happen, we have some good strategies to prevent them,” Pastula said.

The newest theories about the spread of COVID-19 are actually quite groundbreaking, Pastula said.

“Typically, with respiratory illnesses, we usually think of droplets as acting like ballistic projectiles. We previously thought that coronaviruses only spread through these droplets.”

Droplets are relatively heavy. So, when a person sneezes or coughs, the “projectile” droplet is pulled down by gravity within six feet or so and shouldn’t infect people who are farther away. That’s why social distancing — or staying at least six feet apart from other people — is so important. Those who are infected also can sneeze or cough onto their hands, then touch a surface and spread the virus through objects and surfaces.

But, increasing evidence shows that COVID-19 also may travel from person to person via aerosols, much smaller particles that can stay suspended in the air for minutes or hours, and in turn, infect additional people who may be farther away than six feet.

“Aerosols can float. Measles is the classic disease that spreads through the air. It’s so infectious that you don’t need to be exposed to many viral particles to get sick,” Pastula said. “We’ve always thought there’s been a dichotomy. An illness either spreads through droplets or through airborne transmission. But, with this outbreak, we are learning that it may not be black and white. It’s likely that SARS-Co-V-2 may be transmitted through both infectious droplets and short-range aerosols in high enough concentration to cause infections.”

How a choir practice became a superspreader event

Pastula said lessons learned from two particular superspreader events have been critical to boosting knowledge and preventing other events.

“Now that we know more, we have a much better handle on how this virus has spread,” Pastula said

One of the first known superspreader events in the U.S. occurred in Skagit County, Wash. on March 10, where a choir practice at a rented church hall led to mass infections.

“There were 61 people. One of them had a mild respiratory illness that turned out to be COVID-19. This was early in the outbreak, so no one was wearing masks,” Pastula said. “People were seated close together. They were indoors. They were singing and they were together for about two-and-a-half hours. One person is thought to have infected 52 other people in those two-and-a-half hours. That’s a secondary attack rate of 87%.”

Since few people knew then exactly how COVID-19 spread, the choir members didn’t know to stay apart from one another. They didn’t know that singing could be especially dangerous, as could speaking loudly, coughing, sneezing and laughing forcefully. All of those actions could cause an infected person to expel more virus particles farther than they would otherwise. Not everyone who attended the choir practice came into direct contact with the sick person. Therefore, researchers believe the virus also spread through airborne aerosols that floated and traveled throughout the multi-purpose room. Ultimately, two choir members died after contracting COVID-19.

Learning from this tragedy can help prevent other tragedies as long as people remain vigilant, Pastula said.

“We know that there are some activities that aerosolize particles more than others. For instance, we think that quiet breathing or talking with mask wearing is unlikely to generate as many infectious droplets or aerosols. However, speaking loudly and singing, shouting and coughing and sneezing all can generate more infectious droplets and aerosols, especially when masks aren’t used.”

Avoid spending concentrated time inside poorly ventilated public spaces;

This is where Pastula’s simple guidelines for preventing superspreader events come in.

If the choir member who was sick had stayed home, it’s possible no one else would have gotten COVID-19. If the members had been wearing masks, practiced outside, kept their distance from one another or avoided singing in close proximity, the practice also might not have turned into a superspreader event. But again, not as much was known about COVID-19 transmission back in March.

If fewer people had attended the practice or they had been around one another briefly, rather than for an extended period of time, it’s also possible that some might not have gotten sick.

Pastula said people generally need to be exposed to a sick person for at least 15 minutes in order to get infected, though that time may be shorter or longer depending on the intensity of the exposure.

“The longer you spend in proximity to an infected person, the more opportunity you have to inhale infectious particles, whether they be droplets or aerosols,” he said.

Can asymptomatic people trigger superspreader events?

A second superspreader event that has been well studied occurred in January in China and provided evidence early in the pandemic that asymptomatic people still can spread the virus.

A family traveled from Wuhan…

Continue reading here.