Can asymptomatic persons cause COVID-19 community spread? Top doctor clarifies


While Kerala has largely controlled the COVID-19, there have been some worries regarding the asymptomatic cases found in the state and about testing more foreign returnees.

To understand how the government is dealing with such problems, Onmanorama talked to Dr Anish TS, associate professor for community medicine at Thiruvananthapuram Medical College, who is presently posted as public health consultant with the Kerala State Disaster Management Authority.

Edited excerpts from the interview:

The symptoms

Fever is the most common symptom among COVID-19 patients all over the world. While fever is a symptom in 80 per cent of the cases globally, in Kerala only 50 per cent of the patients are showing it. This may mean that we have milder form of infection, but it should be taken seriously. One reason that we are coming across milder symptoms could be because people returning from abroad were mostly youngsters and do not have comorbidities. Cough, running nose and throat pain are some other common symptoms.

Nowadays, some patients are showing a specific symptom called anosmia, which is the inability to detect one or more smells.

Incubation period and infecting others

Incubation period is the time taken for the person to develop signs and symptoms after contracting the infection. We should not misinterpret it as the time till the person is tested positive for the virus.

Usually in COVID-19 the incubation period ranges from 2-14 days. The virus will be present in the body for two or three weeks after showing the symptoms. Suppose you start showing symptoms on the fifth day, the patient may start infecting others from the fourth day onwards. This transmission period or infection period will last only for three or four days. By the tenth day you will stop transmitting the disease but the virus may still be present in your body.

Extended incubation period

In Kerala we have people who showed incubation period of more than 14 days and in some cases we haven’t been able to find out the incubation period at all. To find out the incubation period the patient has to develop signs and symptoms, but there are cases where people show no signs and symptoms.

What we need to understand is that if the incubation period is extended, that means the infection is not of a severe nature and the disease that will be developed is also going to be of a mild nature.

Should we test all foreign returnees?

If you have more resources then one may test all the people after quarantining them, but in India we do not have that much resources. Hence, it may not be a good option to test all the people completing the quarantine period. From a management point of view, if they are not developing any signs or symptoms within 14 days, they are likely to have a mild infection and may not transmit the disease to others.

Was home quarantine effective?

It depends on the people and the state, in Kerala home quarantine has been very effective because of our strong community network. Our past experiences tell us that the neighbourhood groups, volunteers, police and local self-help governments etc will help us to quarantine the people within their houses. This kind of networks may not be available in other countries and they might have to go for an institutionalised approach.

Could asymptomatic cases be spreading the virus?

The asymptomatic cases will not cause a big problem epidemiologically, because they carry less amount of virus and the transmission rate from the asymptomatic persons is going to be less. Mainly, coronavirus is transmitted by the symptomatic persons.

However, an asymptomatic carrier of coronavirus may severely infect an elderly person or someone with other comorbidities. This points to the importance of universal use of masks and hand wash. More so if you are coming in contact with elderly or people suffering from other ailments. Even though, you may not have symptoms you should behave like you have COVID.

We cannot assume how many asymptomatic cases are there in Kerala, because one of the testing criteria is symptoms.

How can we be sure there is no community spread?

We cannot be sure there is no community spread, but there are surrogate evidences. If there is a community spread, then there will be increasing cases of pneumonia, respiratory diseases being reported from Kerala. We can see from other countries what happens when there is a community spread.

We are testing some of the pneumonia cases being reported in big hospitals and medical colleges. We haven’t observed many cases of severe acute respiratory infections with COVID among them. These are evidence that there is no rampant community spread in Kerala.

We will soon have rapid testing kits and with that we may be able to address this question more effectively.

Is the testing method foolproof?

There is a chance that the test results throw a false negative. Which is why it is important that before discharging the isolated from hospitals they have to be tested negative at least twice.

However, the chance of a false positive is much lesser.

Can those recovered from COVID-19 be infected again?

Yes, it is possible. There are many evidences for it from China and Europe. If the initial infection was of a mild kind, then it is likely that the same person can be infected again. However, if a person who was severely infected and recovered from COVID-19, it is unlikely that she will catch the disease again as she has developed the immunity.

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