How can you contract COVID-19? Experts agree on leading cause
As the coronavirus pandemic has sickened over 9 million people worldwide, there has been growing consensus on how the disease gets transmitted, The Wall Street Journal reported. Although general precautions have focused on staying indoors, hand washing, keeping one's surroundings clean, etc., the major reason is apparently close, person-to-person interactions for prolonged periods. Here's how that changes things for us.
Wide-scale lockdowns prevented millions of infections, deaths
Studies have found that wide-scale lockdowns that included stay-at-home orders, bans on large gatherings, business closures, etc., prevented millions of infections and deaths around the world. According to WSJ, scientists also say that it is uncommon to contract COVID-19 from contaminated surfaces. Chiefly, transmission occurs upon close contact through seemingly benign activities such as speaking and breathing, that produce respiratory droplets.
Risk of infection increases on prolonged, close contact
Prolonged exposure to infected persons can raise the risk of infection. Generally, that's defined as over 15 minutes of unprotected contact with someone less than 6 feet away, said John Brooks, the US Centers for Disease Control and Prevention's (CDC) chief medical officer for COVID-19 response. But infection could take less time, say if an infected person sneezes directly in one's face, Brooks said.
Transmission through surfaces not as common
Respiratory droplets commonly fall to the ground or on other surfaces quickly. But, it is uncommon to contract COVID-19 through infected surfaces. Erin Bromage, a University of Massachusetts Dartmouth associate professor of Biology, told WSJ that although cleaning surfaces and putting in hand-sanitizer stations in workplaces is good, the bigger risks are close-range face-to-face interactions, and crowding in enclosed spaces for long periods.
'Shouldn't spend half our budget on surface cleaning'
"Surfaces and cleaning are important, but we shouldn't be spending half of our budget on it when they may be having only a smaller effect," Bromage said. CDC guidelines suggest discarding communal snacks, water coolers, etc., and placing plastic partitions between desks within 6 feet.
At workplaces, break rooms, locker rooms, etc., cause of worry
At the production facilities of drugmaker Eli Lilly & Co., scientists normally wear multiple layers of personal protective equipment (PPE). Lilly Chief Scientific Officer Daniel Skovronsky told WSJ that break rooms, locker rooms, and security checkpoints, where people interact, are the worrisome areas. The firm has instituted measures to promote physical distancing such as reduced cafeteria seating, and using only half the bathroom stalls.
Better ventilation to curb aerosol transmission
Another means of transmission is through aerosolization of the virus, which occurs when the virus floats in minuscule respiratory droplets that can remain suspended in the air for longer and can be inhaled directly. Hence, experts stress on sufficient ventilation to dilute the amount of virus in the air, keeping windows open, etc. However, the virus does not seem to spread widely through air.
Here's an example of possible transmission through aerosols
At a restaurant in Guangzhou, China, an infected patron transmitted the virus to five others at adjacent tables, despite not being ill at the time. A non-peer-reviewed study that analyzed the conditions at the restaurant pointed to poor ventilation. The exhaust fans were turned off and an air-conditioning unit on the wall may have helped recirculate the viral particles from breathing or speaking.
How safe are indoor spaces?
Several studies state that the attack rate (percentage of people who were infected in a specific place/time) of the virus ranges from 4.6% and 19.3% in households. This rate is higher for spouses (27.8%) compared to other household members (17.3%). Experts say being outdoors is generally safer, as the viral particles dilute more quickly, so long as prolonged physical contact with others is avoided.
What makes a superspreader?
The co-existence of multiple conditions facilitating transmission can lead to "superspreader" events. For example, at a church choir practice in Washington on March 10, 53 out of 61 attendees were infected. Members of the choir changed places four times during the 2.5-hour-long practice, were tightly packed, and were mostly older, epidemiologist Lea Hamner told WSJ. Singing also produces many large and small respiratory particles.
Experts warn about places with similar settings
Experts warn about places with similar settings—tightly closed spaces involving heavy breathing or loud talking/singing for extended periods—that could lead to superspreaders. Places with such dynamics could include gyms, musical or theater performances, etc.
How much virus does it take to cause infection?
Importantly, it remains unknown how much of the virus it takes for someone to get infected. A Nature study said researchers were unable to culture live coronavirus if the patient's throat swab or milliliter of sputum contained less than one million copies of viral RNA. One of the study's lead author, Clemens Wendtner, conjectured that "something above that number would be required for infectivity."
