Coronavirus: What It Is and How It Spreads

Coronaviruses are a family of viruses that can infect humans, birds, and other mammals. In people, the infections can range from cold- or flu-like symptoms to respiratory infections, and in some cases severe multi-organ failure leading to death. Coronaviruses were responsible for the Severe Acute Respiratory Syndrome (SARS) epidemic in 2002–2003, the Middle East Respiratory Syndrome (MERS) in 2015, and the most recent respiratory outbreak that began in China.

Why it's called “coronavirus”

The coronavirus family is often divided into four subgroups: alpha, beta, gamma, and epsilon. The newest one does not yet have a subgroup name and is simply labeled a novel (meaning new) coronavirus. The virus gets its name from its appearance: numerous spike projections cover its rounded surface, giving it the look of a crown, or “corona” in Latin. The virus uses these spikes to latch onto the cells it infects. Once attached, it hijacks the infected cell's internal machinery to make new viruses, spreading the infection through the host.

Mild versus severe coronaviruses

Some coronaviruses are common in humans and do not cause severe illness — instead they cause upper-respiratory problems such as the common cold, sore throat, and fever. Even these, however, can cause serious illness like pneumonia in people whose immune systems are weakened.

The coronaviruses that caused MERS, SARS, and the novel coronavirus are different. They are found in animal hosts such as bats or camels before making their way to humans, where they can cause severe infections.

How it spreads

Once a coronavirus moves from its animal host to humans, person-to-person transmission usually occurs through respiratory droplets from a cough or sneeze. Typical surgical masks are unlikely to fully block these droplets, but handwashing helps, since the virus can also be found on many surfaces. The novel coronavirus is believed to be a beta-coronavirus that originated in bats, likely passing to humans through an intermediate animal host.

Symptoms and treatment

After exposure, symptoms can take anywhere from a few days to about two weeks to develop — which is why recent travelers from affected regions have been asked to quarantine for that period. Early symptoms include cough, fever, and shortness of breath.

Treatment is mainly supportive, since there is no specific antiviral medication for it. Supportive care includes fluids, rest, and medicine to manage fever and shortness of breath. Patients who develop more serious complications such as pneumonia or organ failure receive supportive treatment directed at those organs.

Because the novel coronavirus is new, there is still limited information about who is most at risk for the severe form of the illness. Based on past viral outbreaks, the very young and the older population are generally believed to be most vulnerable.