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New Delhi: About 80 per cent of Covid-19 patients in India are asymptomatic, an internal analysis by the Integrated Disease Surveillance Programme (IDSP) has concluded after extensive discussions with states, ThePrint has learnt.

The last documented estimate on this was 28 per cent, published in a study in the Indian Journal of Medical Research (IJMR) in May that looked at cases until 30 April.

Of the symptomatic patients, analysis of all cases until 23 August shows, about 25.93 per cent reported with fever, 17.18 per cent with cough, 7.83 per cent with sore throat and 5.54 per cent with breathlessness, sources said.

However, the largest proportion is of people who reported with other symptoms such as gastrointestinal problems, loss of smell and taste and body ache, added the sources.

“This is an analysis we have done of all the symptoms that patients have reported with. However, it is important to understand that after many meetings with states, it is now clear that about 80% patients in India are asymptomatic. This is a large number,” said a senior IDSP official, who did not wish to be named.

“We earlier thought that these are presymptomatic people who have been traced and tested during the contact tracing exercise and are essentially presymptomatic, that is they go on to develop symptoms later. However, states have now emphatically told us that these are asymptomatic people not presymptomatic. This is the largest chunk of patients,” added the official.

As of Sunday, India recorded 30.44 lakh Covid cases and 56,706 deaths.

Also read: Delhi conducts more antigen tests than 5 top Covid-hit states despite questions on strategy

Asymptomatic patients driving the epidemic

A large number of asymptomatic patients are widely recognised as a pool for further spread of the disease.

Younger people who are in their 20s, 30s and 40s often tend to be asymptomatic and are, hence, the drivers of the disease, the World Health Organization (WHO) said this week. Analysis of data from the top five high burden states in India also bears this trend.

Initially, asymptomatic patients were estimated to be in the 69-80 per cent range in India. Dr Raman Gangakhedkar, former head of epidemiology, Indian Council of Medical Research (ICMR), had given the 80 per cent figure in one of the Covid briefings in April, only to revise it to 69 per cent a few days later. There was a sharp downward revision in this after the IJMR study of over 40,000 patients in May.

However, India’s testing strategy banks heavily on whether a person shows symptoms. According to experts, this is so because a person is less likely to test positive unless symptoms are showing. This is provided a person is presymptomatic, which is a transient phase, and not asymptomatic — a condition that can last the duration of the infection.

With such a high incidence of asymptomatic cases, this may need to be revised at some point.

Also read: Severity of respiratory illness predicts early death of Covid patient, not comorbidity — study

Analysis of signs

The IDSP also analysed the signs as reported by doctors in their forms.

“Symptoms are the complaints that patients come to us for; signs are what doctors discover during their examination,” explained the IDSP official quoted above.

This shows that 8.46 per cent doctors reported an abnormal lung X-ray or CT scan, 2.78 per cent reported tachypnea or rapid breathing, 1.89 per cent reported abnormal lung sounds, 0.75 per cent reported redness of eyes, 0.66 per cent wrote coma, 0.51 per cent reported seizures and 0.60 per cent reported abnormal sounds.

The IDSP official explained that while the reporting form is periodically updated, a lot of the newer signs and symptoms have not been included and are in the process of being added. These include dehydration, alteration of acid base balance of the body, abnormal heartbeats etc. These have all been categorised as “other signs” that constitute 83.54 per cent of the reported signs.

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