Understanding the coronavirus

'The R0 value for coronavirus is neither high nor low'


Dr Pavithra Venkatagopalan was fascinated by the family of coronavirus because of its ability to make RNAs without DNAs. Her doctoral thesis was on a structural protein called envelope protein and its role in virus assembly. She holds a PhD in coronavirus studies from Arizona State University.  

Coronavirus is the same as SARS and MERS structurally, says Venkatagopalan. Currently, she is the director of Care Health Diagnostic Lab, Chennai. 

In an interview with THE WEEK, she speaks about how potent coronavirus is and also about the chances of people getting infected by touching contaminated surfaces. 

Excerpts from the interview: 

How contagious is coronavirus? 

Contagious means how effectively it spreads from one person to another. 

Coronavirus infects efficiently. How contagious a virus is depends on its R0 value, which is the number of persons an affected person can infect. A person infected with coronavirus can typically infect 3-4 people. The R0 value for this virus is neither high nor low. It falls somewhere in the middle when you look at it statistically. It is in between.  

R0 value of poliovirus was six before the vaccine was invented. So every infected person was capable of infecting six people. The spike protein of the SARS Coronavirus 2, the virus that causes COVID-19, binds strongly to the cellular receptor that the virus uses to enter the cell. Since the binding is strong, the number of viral particles needed to infect a single cell is less. So it will very quickly enter the cell. 

Around 76 per cent of COVID-19 patients in Karnataka are asymptomatic.  

Coronavirus infects very stealthily. If a person has obvious symptoms like measles or chickenpox, they obviously look like they are infected. So others will take care not to go near them. But coronavirus spreads when a person has no symptoms also. The virus is very clever and it may not always be possible to isolate the patient, as the symptoms may not always be manifested.  

Does the virus spread from surfaces? 

The virus is not aerosol-based. It is a droplet-transmitted infection. There have been numerous studies on how they survive on various surfaces for a long time. I studied a research paper on it. The conditions scientists use in a lab are not what you would see in real life. Scientists put a drop of the virus on a surface and let it sit at 21 degree C in an environment with 30-40 per cent humidity and see how long it can survive. In real life, you will see small splashes of the virus that come from our saliva and sneeze.

Also, the temperatures around us are higher than 21 degrees C especially in Central and Southern India. So the chances of this virus spreading from surfaces are quite low. This doesn't mean you don’t have to take precautions. Do wash your hands frequently. Until the droplets dry, the virus is still active and if you touch your nose, mouth or face after being in contact with a contaminated surface, you could still get the infection.