69% of cases found positive were asymptomatic: ICMR

NEW DELHI: Covid-19 tests that delivered positive results in India so far show 69% positive cases were asymptomatic, whereas 31% are symptomatic representing a ratio of 1:2, the Indian Council of Medical Research (ICMR) said on Tuesday. So far, over four lakh samples have been tested for Covid-19 in India and of these 18,601 were positive.


ICMR head of epidemiology and communicable diseases Dr R R Gangakhedkar said, “There is only one study that suggests there are 80% cases. Secondly in case of asymptomatic, where the symptoms are not very clear, the chances of patient coming and reporting the case too becomes low. I am now saying for the first time that if we look at the number of tests done, so far 31% belong to the symptomatic category and the rest 69% would fall under asymptomatic...we can say that for every single case detected there would be about two cases that may be termed as asymptomatic.”


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Seeking to address concerns over asymptomatic cases, the health ministry said they include those with mild and sometimes “very mild” symptoms and efforts are on to identify such cases through contact tracing and community surveillance. Citing observations of the WHO, health ministry joint secretary Lav Agarwal said there are three phases : purely asymptomatic, pre-symptomatic and symptomatic, and in common parlance even pre-symptomatic cases are called asymptomatic when the symptoms are mild.

“We are working with a pre-emptive approach while working on community surveillance. If we find a so called asymptomatic case in a field with high risk or direct contact, then we collect even that sample for testing. In that case, when a person has even mild symptom, the test is positive. This way we can timely identify and reduce mortality,” Agarwal said. Officials said there is a probability that there are several asymptomatic persons who may not know that they carried the virus for a while, but the numbers so far are not seen to be so high as to represent a threat of undetected transmission on a significant scale. If that were to be the case, there would be a higher number of positive cases as well who needed medical attention. The official also added that the testing strategy is not static and if more attention was needed in the case of asymptomatic persons, the protocols would be revised afresh.

According to WHO, pre-symptomatic period is the incubation interval for Covid-19 — between exposure turning into infection and symptom onset. This period is on average five to six days but can be up to 14 days. During this period, some infected persons can be contagious. Therefore, transmission from a pre-symptomatic case can occur before symptom onset. A truly asymptomatic case is a confirmed case in a person infected with Covid-19 who does not develop symptom.