The modus operandi is becoming clearer. For the most part, SARS-CoV-2, the coronavirus that causes Covid-19, spreads by close personal contact via tiny particles emitted when an infected person coughs, sneezes, speaks, sings — or even just breathes normally. These can infect another person by falling into an eye, nose or mouth, by being inhaled or getting stuck on a hand and transferred to one of these entry sites. Here’s an explanation of the established route of contagion and other pathways under investigation.
These spatters of virus-laden liquid of varying sizes, expelled from an infected person in a turbulent gas cloud, are thought to be the main route.
The warm, moist atmosphere within the gas cloud delays evaporation, while airflow helps propel the payload of pathogen-bearing droplets further than if they were outside a cloud. A cough can disperse virus particles 4-to-5 meters (13-16 feet) and a sneeze can project them as far as 8 meters away, depending on humidity and temperature. Infection could occur if the droplets drift into the nose, mouth or eye of someone nearby.
Droplets can contaminate surfaces when they settle, creating what’s called a “fomite.” Although less likely, transmission could occur when a hand touches a fomite, such as a doorknob or utensil, and then comes in contact with the mouth, nose or eyes.
Patients may harbor potentially infectious SARS-CoV-2 virus in their saliva, stool, and urine as long as 15 days after falling ill, researchers in South Korea showed in a study of five patients in July. Spending at least 15 minutes in close contact (being within 1.8 meters) with an infected person, and spending even briefer periods with someone who is coughing or sneezing, are associated with higher risk for transmission.
The virus can be highly stable in favorable environments, lingering for weeks in near-freezing temperatures. At room temperature, it can survive as long as 24 hours on cardboard, 48 hours on stainless steel, and 72 hours on plastic, one study found. Standard disinfection kills it though.
Public health authorities recommend people wash their hands frequently, avoid close contact for prolonged periods with those outside their household, and forgo shaking hands, hugging and kissing for now. For households with a suspected or confirmed case of infection, doctors suggest keeping that person separated from others as much as possible and cleaning and disinfecting “high-touch surfaces” in common areas — such as switches, tables and remotes — daily. Where members of the public are crowded together, such as on buses and subways, numerous health authorities across the world are telling people to cover their faces. If medical masks are in short supply, many suggest using home-made versions.
Tiny Aerosolized Particles
The tiniest particles emitted from an infected person may be carried aloft in gas clouds tens of meters from where they started. Indoor and closed environments without adequate ventilation and air-filtration enable these microdroplets to float longer, while their small size increases their odds of being inhaled, causing a potentially more severe infection. Evidence for airborne transmission is still emerging, however, and incomplete…Read more>>