Hot spots and super-spreaders

The role of hot spots and super spreaders in the pandemic

June 4, 2020 

Hot spots and super spreaders

Here’s a few examples:

As the nation begins to get a handle on the Covid-19 pandemic, two very unscientific-sounding terms are being used to describe the next worries for health officials and health care workers on the frontlines: “super spreaders” and “hot spots.”

“The danger with this virus is that a person can be asymptomatic, or have mild symptoms and be very contagious,” said Dr. Paul Cook, Chief of Infectious Diseases and Professor of Medicine at the Brody School of Medicine at East Carolina University.

“That’s why staying at home, social distancing and avoiding group gatherings, hand washing, mask wearing, and covering your cough are so important.”

“Most of the country has reached a plateau with the virus,” adds Cook, “but if people let down their guard the virus will come roaring back led by super spreaders creating hot spots.”

What does a super spreader do?

Here’s what happens. Illinois health officials reports that back in February, friends and family members gathered for the funeral of a man who died of causes unrelated to coronavirus. Among the attendees: a close friend of the family who had recently traveled out of state and was fighting mild respiratory symptoms. The man, and the rest of the gathering, shared tears and stories and hugs as well a potluck meal.

Three days later, the same group of family and friends gathered again, this time for a birthday celebration. The man was still battling respiratory symptoms. Days later, because he wasn’t feeling any better, he went to a doctor and was tested for Covid-19. The tests came back positive.

The man recovered but by then, he had already passed the virus to others. In all, 16 were infected. Three died.

The case study was reported April 8 in the U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.

What makes someone a super spreader?

The term “super spreader” isn’t a medical term. It refers to someone who is spreading contagion at a much greater rate than the average infected person. That’s right, super spreaders spread a virus more efficiently than most people.

The term can change depending on the virus. The CDC reports during the SARS (severe acute respiratory syndrome) outbreak in 2003, a super spreader was considered someone who directly infected 10 or more people. The normal infection rate was one index case directly infected 2.75 people. With the coronavirus that causes Covid-19, the traditional spread is one index case is directly linked to 1.5-3.5 people.

Because this virus is so new, there’s no definition yet of a super spreader.

Is there a medical issue connected to super spreading?

There is no medical evidence that one person is more able to pass on a disease that someone else, but there are a number of factors that make someone a super spreader. Some of those factors are biological.

Because Covid-19 is known to spread through droplets; a person who is sick and coughs violently and frequently could be a super spreader by infecting more people. In addition, if the person’s immune system is compromised, they may not recover as quickly and keep spreading the infection longer.

Then there’s simply chance. A person might meet a lot of people, either because of where they live or if they encounter large groups. All of that increases the chance of spreading the infection to more people.

“Super spreading is a medical factor and a social factor,” explained Dr. Cook. “We’re all connected because we all have family, friends and co-workers. While some people are more connected than others, if you aren’t social distancing and wearing a mask, you could easily become a super spreader and possibly create a hot spot without realizing it.”

Super spreading and hot spots

Hot spots are the other concern. Just like “super spreaders,” the term "hot spot" is not a public health term but it describes an area with a particularly large cluster of cases. It’s all about a high density of people.

So, if a super spreader works in a factory with a large number of people in a tightly packed area, or if a super spreader visits a place with a large number of people packed closely together (a concert, sport event) that could create a Covid-19 hot spot.

Health officials use graph theory, where each person is thought of as a "node" that is connected to other people—friends, family, colleagues—by links, to model super spreading and hot spots. It’s kind of like a social network: Every person has links to friends and family and co-workers. Everyone is "connected" to others to a greater or lesser extent.

There is an average number of relations for any person in that network, but there are people with extraordinary degrees of connectedness. Those are the super spreaders. And if an infected person becomes “connected” to people by virtue of being in the same densely packed place, that can create a hot spot.

“The best way to show we care for each other is by keeping apart, wearing masks, and doing all we can to stop the spread of the virus,” Cook adds. “Because in any extended gathering, it’s likely someone will be among those at high risk for severe infection and death from the virus.”

—Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on Sci NC, a broadcast and online science series.