Source: Snopes.com/TheConversation.com, Your HHRS News
When people cough or talk, they spray droplets of saliva and mucus into the air. Compared to most other viral infections, the coronavirus produces an unusually high level of viral particles in the upper respiratory tract, specifically the nose and mouth. When those viral particles escape into the environment, that is called viral shedding.
When people get sick from the coronavirus, it takes on average five days and as many as two weeks to develop symptoms that can range from very mild to extremely dangerous. Researchers have found that pre-symptomatic people shed the virus at an extremely high rate, similar to the seasonal flu. But people with the flu don’t normally shed virus until they have symptoms.
The time between initial infection and the first symptoms is called the pre-symptomatic phase. Estimates of the proportion of true asymptomatic cases — those who are infected and never develop symptoms — range from 18% to over 80%. A recent paper compared the evidence from 16 studies and estimated the overall rate of asymptomatic infection to be 40%-45%.
Even without knowing the exact numbers, the Centers for Disease Control and Prevention (CDC) believes that transmission from people without symptoms is a major contributor to the rapid spread of SARS-CoV-2 around the world. On April 3, the CDC recommended that all members of the public wear facial coverings when outside of the house and around others. Two months later, the World Health Organization (WHO) followed suit and recommended universal public masking.
But while masking and social distancing can therefore prevent asymptomatic spread and help reduce the harm from this dangerous virus until we get a vaccine, it is only part of the solution.
The most accurate way to determine the rate of asymptomatic cases is to test people regardless of whether or not they have symptoms – an approach called universal mass testing – and track them over time to see if they develop symptoms later.
A recent mass testing campaign in San Francisco found that 53% of infected patients were asymptomatic when first tested and 42% stayed asymptomatic over the next two weeks. The time has come to isolate and quarantine such patients more comprehensively to prevent not only further spread of the virus, which will in turn also prevent it from mutating and ultimately weakening the immune systems of everyone.