This article was originally published on January 27, 2020.
In January, the World Health Organization declared a Public Health Emergency of Global Concern due to the rapid spread of the novel coronavirus. Since then, there have been confirmed cases of the illness, now known as COVID-19, in most countries around the world, and the U.S. currently has the highest number of confirmed cases per country.
What is COVID-19?
COVID-19 is an illness caused by a type of coronavirus called SARS-CoV-2. According to the CDC, the illness is spread primarily from person-to-person through respiratory droplets when an infected person coughs, sneezes, or talks. The spread is more likely when people are in close contact (within about six feet) of one another, especially when people aren’t wearing personal protective equipment, like cloth face coverings. In a fact sheet released in April, the CDC noted that the illness may also spread “by touching a surface or object that has the virus on it, and then by touching your mouth, nose, or eyes.”
Generally, symptoms such as coughing, shortness of breath, and fever appear between two and 14 days of infection. But these symptoms can vary from person-to-person, and they aren’t always respiratory. “What is very clear now is that it’s a multisystemic disease,” says Edward Charles Jones-Lopez, an assistant professor in medicine specializing in infectious diseases at Keck Medicine of USC. "It can affect basically any organ of the body." Jones-Lopez says doctors aren’t yet sure why some people experience respiratory symptoms, like shortness of breath, while others experience “severe manifestations,” like blood clots and stroke. And many infected people may have no symptoms at all.
“It has been established that this virus spreads easily and effectively, and we are learning that up to 50 percent of positive cases present with no symptoms or mild symptoms,” says Melissa Hawkins, an epidemiologist and director of the Public Health Scholars program at American University. “Those with no symptoms are sometimes referred to as ‘silent carriers,’ and tend to be younger and healthier than those who present with severe symptoms.”
People with chronic illnesses like diabetes or heart or lung disease could be at a higher risk for developing COVID-19 complications, but anyone can get sick from it.
How is it diagnosed?
According to Amesh Adalja, an infectious disease physician and senior scholar at the Johns Hopkins University Center for Health Security, COVID-19 is diagnosed using a nasal swab or saliva test that looks for genetic material of the novel coronavirus in a person who has clinical symptoms, or has been exposed to an infected person. If a health care provider finds genetic material of the virus present on the swab, a person will have a positive result.