“Super-Spreaders”: How Fatal Mistakes Can Lead to Massive Outbreaks

A recent report from the New York Times reveals new information on the spread of the coronavirus. As it turns out, most people are unlikely to pass the virus onto others, especially if they’re wearing a face mask or keeping to themselves. This has slowed the spread in many parts of the world, but with summer heating up, experts now warn of potential “super-spreaders,” or those that pass the virus onto 10 or 20 other people.

This has complicated our country’s response to the pandemic over the last few weeks and months. Even if most people are adhering to the latest safety guidelines, a few bad apples can derail this progress in a matter of hours if they’re not careful.

Calculating the Reproductive Number

All viruses and infectious diseases come with what’s known as a “reproductive number,” or the estimated number of people each sick person infects. As soon as the pandemic started flaring up in China in late 2019, health experts started tracking the spread to come up with an estimate. It is now believed that the novel coronavirus comes with a reproductive number of two to three. That means every sick person infects an average of two to three people.

However, this number tends to vary widely across the globe. In the U.S., states and cities have lowered this number with the help of social distancing, sheltering-in-place, and mandating that everyone wear a face mask when going out in public. With these steps, Massachusetts was able to go from a reproductive rate of 2.2 at the beginning of March to a rate of one by the end of that month, often considered the height of the pandemic. The state now has one of the lowest reproductive numbers in the country with just 0.74.

Varying Rates of Exposure

Some diseases, like influenza, tend to linger for months or years on end as one person infects several others at a time, but the novel coronavirus seems to be prone to random flare-ups. One person can easily infect dozens of others if certain factors come together.

In some ways, the average reproductive number can be misleading. Many people may not infect anyone at all, while others expose themselves to large groups and crowds. This could send the reproductive rate soaring, even if many people aren’t spreading the virus.

Dr. Adam Kucharski, an epidemiologist at the London School of Hygiene and Tropical Medicine, and his colleagues discovered wide variations in terms of the spread of the virus. In a recent study, they showed that 10% of infected people were responsible for 80% of new infections. While the study has yet to be peer-reviewed, other epidemiologists have reached similar conclusions.

In Georgia, researchers tracked the spread of the disease across five counties. As it turns out, just 2% of people were responsible for 20% of infections.

So, Who Are the Super-Spreaders?

Scientists are still trying to pinpoint exactly what types of people are responsible for these massive outbreaks. Some believe the virus is replicating faster in certain people who may expose others every time they take a breath. Others say it is more circumstantial.

Regardless, it all comes down to how many people these individuals interact with on a daily basis. If someone works at a grocery store, they are much more likely to spread the virus than someone working from home. Attending large gatherings, crowded spaces, and taking public transportation will also increase a person’s chances of becoming a super-spreader.

However, many people can go about their lives without infecting anyone. They may work from home or drive to the office, shop for groceries, and call it a day, thus minimizing their risk of exposure. But those working in the public sector or high-traffic areas can easily infect dozens of others. Bars, restaurants, gyms, nursing homes, and day care centers have also been linked to numerous mass outbreaks.

Studies also show that most people spread the virus a couple of days before symptoms appear, serving as a reminder that it’s important to stay safe even if you feel healthy.

Health officials are using this information to warn governments around the world that things can easily fall apart if we let our guard down by lifting safety restrictions or reopening too fast. As Dr. James Lloyd-Smith, a U.C.L.A. disease ecologist, says, “You can really go from thinking you’ve got things under control to having an out-of-control outbreak in a matter of a week.”

Hope for the Future?

Super-spreaders may end up working to our advantage. If most infections can be traced back to a select number of people or events, cities and states can do more to prevent these kinds of outbreaks from happening, such as by mandating face masks when in public, limiting or outright banning indoor dining and drinking, and preventing house parties and large gatherings.

We don’t have to shut everything down again to get back to normal. It’s just about taking certain precautions and taking personal responsibility. Talk to your patients about “super-spreaders” and help them avoid becoming one themselves, so we can contain the virus as much as possible.