How long you are exposed to coronavirus can determine if you get sick, experts say
As the novel coronavirus continues to spread around the world, experts are trying to understand all the factors that play a role in virus spread, infection and severity.
Now, experts are dipping their toes in an idea that isn’t particularly new in the infectious disease community, but that lacks sufficient research surrounding the novel coronavirus — the longer a person remains in a contaminated environment, the more likely they are to get sick with COVID-19, the disease the virus causes, and in some cases, the worse their illness can become.
“The longer time you spend in that environment — so minutes or hours in there — the more virus you breathe in, the more it can build up and then establish infection,” Erin Bromage, a comparative immunologist and biology professor at the University of Massachusetts Dartmouth, told CNN. He wrote about the concept in a blog post earlier this month.
“So it’s always a balance of exposure and time,” he told CNN. “If you get a high level of exposure, it’s a short time (to infection, and if you get a) low level of exposure, it’s a longer time before that infection can establish.”
Bromage invented an equation to summarize the phenomenon: “Successful Infection = Exposure to Virus x Time.”
Duration of exposure matters because the longer someone is coughing, sneezing, talking or even breathing in a closed environment, the higher the viral load in the area.
Viral load refers to how many virus particles are inside people’s bodies or any given area at a certain time, according to Stat. Usually, the higher the load, the worse the damage or symptoms.
A 2015 study showed that the higher the dose of Influenza A virus given to healthy volunteers, the worse their symptoms became, according to the peer-reviewed paper published in the journal Clinical Infectious Diseases.
This means that healthcare workers are more at risk of contracting SARS-CoV-2 — the coronavirus driving the pandemic — and developing harsher symptoms because they are exposed to sick patients in a closed space for hours at a time.
“Someone caring for large numbers of patients on the wards, if they’re not wearing personal protective equipment, there might be a high frequency of exposure as well as a high dose of exposure,” Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston, told Stat.
A grocery shopping trip, on the other hand, would carry a lower risk of infection because exposure time is much shorter, Bromage told CNN.
To figure out how much exposure time is too much or just enough to get infected, researchers would need to inject live viruses in healthy people, which is unethical, CNN reported. The 2015 study involving Influenza A virus is considered rare.
“Data are insufficient to precisely define the duration of time that constitutes a prolonged exposure,” the Centers for Disease Control and Prevention said. “Recommendations vary on the length of time of exposure but 15 min of close exposure can be used as an operational definition.”
“Brief interactions are less likely to result in transmission; however, symptoms and the type of interaction (e.g., did the person cough directly into the face of the individual) remain important.”
Other factors play a role, too, such as who is around to get infected. Some individuals have weakened immune systems from underlying health conditions that increase their risks.
Loud environments including restaurants and nightclubs are also more likely to harbor viruses that can linger in the air.
Research has shown that just one minute of loud speaking could generate more than 1,000 coronavirus-containing droplets that could float in the air for 8 minutes or longer, McClatchy News previously reported.
Early in March, a two-and-a-half hour choir practice in Washington state infected 53 of the 61 attendees with COVID-19 because of one sick person.
Experts say the loud singing, together with a lack of social distancing and amount of time spent rehearsing, likely contributed to the intense spreading event.
This story was originally published May 19, 2020 at 3:48 PM with the headline "How long you are exposed to coronavirus can determine if you get sick, experts say."
