Delhi on April 13 saw the largest spike of 356 fresh COVID-19 cases and two days later the city recorded its lowest number since the surge in cases here, with experts attributing this "fluctuation in data" to multiple factors, including pace of contact tracing.
The total number of coronavirus cases in the national capital on Wednesday increased to 1,578, with 17 fresh cases and two deaths being reported in a day, taking the death toll in Delhi to 32, according to Delhi government authorities.
Of the total cases, 1,080 were those who have been brought to facilities through special operations.
Government authorities had last month carried out measures to quarantine people who were related to the Tablighi Jamaat religious congregation that took place in Nizamuddin area in March.
On April 10, the city recorded 183 fresh cases, including 154 from Markaz in Nizamuddin. Till April 15, the new infection counts recorded per day stood at -- April 11 (166), April 12 (85), April 13 (356), April 14 (51) and April 15 (17).
Vikas Maurya, Director and Head, Department of Pulmonology and Sleep Disorders, Fortis Hospital, Shalimar Bagh, here, says relative rise and fall in fresh cases being reported is among other factors also due to varied contact tracing over a period of time.
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"If you look at the initial spike, it is clear that most cases are from the Nizamuddin area after that religious congregation. And contact tracing of people who may have contacted the disease takes time, so, those cases reflect later then once the test results are out, which take 4-5 days," he said.
Maurya said even those people who had come from abroad and infected others, including their family members, and were not telling authorities such cases and their contact tracing is also a reason why the cases are fluctuating.
"But good thing about the fluctuation in cases is that it means the infection has not gone to community level in Delhi. Otherwise, the fresh cases would have only steadily increased," he claimed.
Two kinds of diagnostic tests have been prescribed for use in India -- RT-PCR test and rapid antibodies test, as per the global health norms.
While RT-PCR test is being used currently, rapid anti-bodies test kits are still awaited from abroad, experts said.
"If the rapid anti-bodies tests begin, our screening process will get expedited and more cases can be traced and detected in shorter period of time," said another expert at a leading private hospital, who did not wish to be identified.
A reverse transcription-polymerase chain reaction (RT-PCR) test is a laboratory technique combining reverse transcription of RNA into DNA that detects the virus while the antibody tests, which use blood, detect the body's response to the virus.
"The rapid anti-bodies test takes less time and results can come in 20-30 minutes. But, till the kits do not come to India, RT-PCR tests are being used in hotspots and other high-risk areas, so results reflecting later, hence the variation in data," he said.
And tracing of people who came in contact with infected people takes time, so people who may have been infected a week ago, their data will be added only later once the results come out, the doctor said.
Delhi so far has 56 containment zones, which have been sealed by authorities.
Sample collection for the high-risk areas in identified containment zones for people who had come in contacts with persons testing positive is being carried out, Delhi Health Department authorities said, adding that 692 samples have been collected till Tuesday.
According to the department, out of the total 1,578 cases recorded till April 15, at least 867 are admitted at various hospitals like LNJP Hospital, GTB Hospital, RML Hospital, Safdarjung Hospital and Rajiv Gandhi Super Speciality Hospital (RGSSH) and AIIMS Jhajjhar, adding that 29 of them are in ICU and five on ventilators.
Out of the total 1,578 cases, 40 have been discharged and one has migrated out of the country, authorities said.
The total number of COVID-19 samples sent till date stands at 16,605. On April 15, the corresponding figure was 11,061.
Experts on Wednesday said that India needs to "significantly ramp up" the number of testing done across the country to trace COVID-19 cases if the pandemic is to be contained in time.
The death toll due to coronavirus rose to 414 and the number of cases to 12,380 in the country on Thursday, according to the Union Health Ministry.
As many as 2,517 people have been kept in quarantine at various government facilities here, the Delhi health department said on Wednesday.
A total of 30,451 people who came in contact with affected persons, are under home quarantine till date and 18,464 have completed their 14-day quarantine, they said.