Coronavirus disease 19 (COVID-19)

Coronavirus disease 19, or COVID-19 for short, is caused by a pathogen called SARS CoV-2, or severe acute respiratory syndrome coronavirus 2.

So from its name alone, “severe acute respiratory syndrome coronavirus,” you get that this pathogen is a type of virus that causes a respiratory infection.

The number two is in the name because this virus is genetically very similar to the SARS coronavirus, which was responsible for the SARS outbreak of 2002.

For someone to become infected with COVID-19, all 6 steps in the chain of infection model must be met.

In order, these include: the pathogen, the reservoir, the portal of exit, the method of transmission, the portal of entry, and, finally, the susceptible host.

So for COVID-19, the pathogen is COVID-19, and the reservoir is a place where the virus can survive. Right now, the natural reservoir for COVID-19 is still being investigated.

Both symptomatic and asymptomatic humans who are infected with COVID-19 can act as reservoirs.

The virus is then released from the reservoir through a portal of exit, like the respiratory tract. Transmission can happen through respiratory droplets.

When people cough or sneeze, they can spread the virus directly to other people, or those droplets could end up on surfaces like phones, tables, doorknobs, and faucets.

The droplets then enter the respiratory tract as well as the mouth or eyes as the portal of entry. Finally, the virus then infects a susceptible host, which is, well, another person.

Once a person is infected with COVID-19, there’s an incubation period, which is the time between infection and symptom development.

For COVID-19, the incubation period can last for up to 14 days but is usually around 4 or 5 days.

Some people don’t develop symptoms at all, but they can still transmit the virus to other people. Others develop symptoms, which can range from mild to severe.