Positivity rate among contacts lower than among general population, shows data submitted to court

The Delhi government informed the court that a total of 19, 54,261 contacts had been traced for positive cases out whom 54,154 tested positive. With 601,150 cases, this means that just over three contacts were traced for every case in the city.

Only 2.77% of the people who were traced as contacts of a Covid-19 patient were found to be positive till date, according to the data submitted by the Delhi government in the Delhi high court. In comparison, Delhi’s cumulative positivity rate – proportion of samples that return positive among those tested – was 8.36% (as on Monday), as per the government data. This is contrary to what experts say -- that the positivity rate should be as high as 50 to 70% among close contacts; for example, those in the same family.

A health worker collects a swab sample from a man for Covid-19 test, at Sector 30 District Hospital, in Noida on Monday. (Sunil Ghosh/HT Photo)

Also, the daily positivity rate had shot up to almost 37% during the first surge in Covid cases in June and July, and up to 30% for RT-PCR tests during the recent November surge.

In a status report filed through the additional standing counsel Satyakam, the Delhi government informed the court that a total of 19, 54,261 contacts had been traced for positive cases out whom 54,154 tested positive. With 601,150 cases, this means that just over three contacts were traced for every case in the city.

The data also showed that very few people – 0.008% or 562 of the 665,513 placed under quarantine – violated it. The data was submitted to a bench of justice Hima Kohli and justice Subramonium Prasad on Monday while hearing a plea by a lawyer Rakesh Malhotra seeking a ramping up of testing in the city.

On Monday, Delhi reported 1,376 new cases of the infection with fewer than the average 63,944 tests. The city also reported 60 deaths due to Covid-19, taking the total toll to 10,074 so far. After reporting fewer than 50 deaths for two days in a row, the numbers went up on Monday.

This has also increased the 10-day case fatality ratio – proportion of deaths among those tested positive – to 2.54%, as per the daily health bulletin.

Dr Shobha Broor, former head of the department of microbiology, All India Institute Medical Sciences said, “The positivity rate among contacts should be much higher than that of the general population. In fact, studies show that it could be as high as 50% to 70% among close contacts such as family members, depending on whether the index patient was symptomatic and also the duration of contact.”

During the hearing on Monday, the bench asked the Delhi government to give the districts which has seen a surge in the number of cases so that testing can be ramped up in these areas. It also sought to know the current situation while also seeking to know whether the government had started a fresh sero survey.

The matter was adjourned on Monday due to the paucity of time and would be now heard on December 23.