69% Asymptomatic COVID Cases: Should India Worry Or There Is Hope?

Dr Sumit Ray speaks to FIT about asymptomatic cases and what it means for India.

Updated24 Apr 2020, 10:22 AM IST
Coronavirus
5 min read

In the last few weeks, a lot has been said about asymptomatic and mildly infected coronavirus cases.

Earlier this week, Lav Agrawal, Joint Secretary, Ministry of Health said, “On the basis of worldwide analysis, 80% of coronavirus patients are asymptomatic or show mild symptoms. Around 15% convert into severe cases and 5% have the possibility of turning into critical cases.”

However, a day later, Dr Raman Gangakhedkar, a senior scientist of the Indian Council of Medical Research (ICMR) clarified saying these results were only from one report. He further added out of these 80% cases, only 69% were asymptomatic.

With this, the speculations about whether or not these people can further transmit the coronavirus silently and will this be dangerous for India in the long run in the absence of enough tests, have risen.

FIT spoke to Dr Sumit Ray, Critical Care Specialist to answer all your questions around asymptomatic and mild infected cases which has been a serious concern for all the other countries as well.

He hints that these cases, in fact, can be a blessing in disguise as it will lead to herd immunity, however, to stop the transmission one should still take all the precautions such as social distancing and face masks.

Here is the transcript of our interview with him.

What Does It Mean To Be Asymptomatic?

The percentage of mild and asymptomatic cases is about 80 percent. Two of the major databases from both China and Italy have shown that that’s the amount of percentage that we see of mild and asymptomatic cases. Asymptomatic cases can only be found out through contact tracing and these are patients who grow the virus on their RT-PCR but do not show any signs of fever, cough, breathlessness, etc, at all for more than a period of 3-4 weeks, so those are the ones who are asymptomatic.

Can Some Asymptomatic Cases Remain Undetected?

Of course, there will be a fairly large percentage of patients who will be asymptomatic and can never be detected.

The Difference Between Pre-Symptomatic & Asymptomatic

The pre-symptomatic ones are those who start getting the symptoms down the line in a few days. So they were in the pre-symptomatic stages but the virus was detected. The asymptomatic are the ones who never get the symptoms.

How Many Asymptomatic Patients Become Pre-Symptomatic?

Well, it’s difficult to say how many asymptomatic patients will turn pre-symptomatic but two interesting studies have happened. One in China and another from the Diamond Princess cruise ship, which was an interesting study because the Diamond Princess cruise ship was like a containment lab for this and they found that about 50% of the patients who were tested turned out to be positive without having symptoms.

They were asymptomatic at the time of the test but over a period of time, almost 75% of those turn out to have symptoms later. So only 25% remained asymptomatic and 75% became symptomatic after a little while.

Why Do Asymptomatic Patients Not Show Symptoms?

Actually that’s a sign that the body’s immune response is working. One is, the viral load wasn’t very large that's why they did not mount a strong immune challenge or the other is that they have a very good immune system that blocked the virus and did not cause any symptom while blocking the virus from causing the disease. So actually mildly symptomatic or asymptomatic cases are a good sign. That means that we have started fighting back and our immune system has started fighting back the virus.

It was predicted by all epidemiological models before also that a large percentage of young people will remain asymptomatic or mildly symptomatic like most respiratory virus illnesses. Only a small percentage gets a more severe or typical symptom and that's a sign that when these young people build up their immunity - this is what is going to build up the herd immunity that we’re talking about and 60-70% of the people have the infection and build an immunity to it then the transmission reduces long term of this viral infection.

Can Asymptomatic Cases Transmit the Virus?

Like symptomatic cases, they start their viral shedding anywhere after 24 hours but predominantly between 3-7 days but can go up to 14 days. The chances of spreading by asymptomatic patients is relatively less. The reason being that the virus is spread through the symptoms. When you cough or sneeze the fomites and the secretions that go out infect the people. So if a person is asymptomatic the chances are less. I’m not saying that it doesn’t happen but the chances of a severe spread of infection are less.

Can Asymptomatic Transmission Be Controlled?

We cannot 100% stop the transmission because of asymptomatic cases from asymptomatic cases but that is the reason why that you need to wash your hands, keep social distancing as far as possible, wear a mask in public and also clean surfaces that are commonly touched and used. So this will take care of all forms of infections, symptomatic and asymptomatic, that is the target.

Can you stop it 100%? No. And you should not stop it 100%. The whole idea at this moment across the world is that some degree of the lockdown and reduced movement of people outside is only to slow the surge and the peak number of cases coming to the health system, so that the healthcare system doesn’t get overwhelmed. But, finally, the infection has to go into the community, cause a build-up of the immunity, build up the herd immunity and then long-term that is the major way in which this COVID infection is going to be stopped or reduced. It can never be completely stopped. It can be reduced. It’s severity and the number of people it infects reduce and that’s the important part. These measures that are being taken now are just to reduce the surge and not completely stop the infection forever, we have to get that out of our heads.

How Worriying Is Asymptomatic Transmission?

When it spreads in the community it builds up immunity and the herd immunity is the best way and not just that. What’s interesting is, and that has happened to a lot of virus and bacteria like the influenza virus or cholera, etc, is that once a large percentage of people are infected, the whole idea of a virus for itself is not to kill people. A virus lives to increase its spread, and its life. If it kills the person it has infected then the chances of its spread actually reduces. So to spread further the virus does not need to kill, it is not going out there to kill you. It is wanting to spread itself like population.

To do that many viruses and bacterias actually become less virulent over the period of time so that they spread more without causing a severe disease and killing less. This is seen in many viruses and bacteria. The possibility that it will happen to COVID in the long run is very high but at the present moment, it is worrying and a dangerous virus because its ability to kill is more than the usual influenza virus that’s why we have to stop the surge but in the long term we have to build a herd immunity which is the Swedish model, the swedes are trying to do. They are actually allowing the spread of the virus among the young and protecting the elderly, keeping them isolated and providing them with daily needs, food, etc so that they are isolated and they are not infected. This may not be possible in India's context with a much larger population but that’s an interesting model to watch.

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Published: 24 Apr 2020, 07:19 AM IST
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