Health experts and doctors have attributed this "sudden rise" in cases to people turning complacent, not following COVID-appropriate behaviour and "assuming all is well now".
Delhi recorded 4,033 coronavirus cases on Sunday, the highest daily count this year, while the positivity rate rose to 4.64 per cent from 4.48 per cent a day ago, according to the health department.
Twenty-one more people died due to the disease, the highest since January 1, when an equal number of fatalities were reported.
The number of cumulative cases stands at 6,76,414 and the death toll is 11,081.
The city had reported 3,567 cases on Saturday and 3,594 cases on Friday.
The last time the city recorded more than 4,000 cases was on December 4 when 4,067 people were diagnosed with COVID-19.
Delhi had reported 2,790 cases on Thursday, and 1,819 coronavirus cases on Wednesday, 992 cases on Tuesday, 1,904 cases on Monday and 1,881 cases on last Sunday.
The number of active cases rose to 13,982 from 12,647 a day before.
A total of 86,899 tests, including 54,472 RT-PCR tests, were conducted a day ago, the bulletin said.
The number of people under home isolation rose to 7,144 from 6,569 a day ago. The containment zones rose to 2,917 from 2,618 on Saturday, it said.
Of the 6,139 beds set aside for coronavirus patients in government and private hospitals in Delhi, 3,404 are unoccupied, according to government data.
Earlier this week, 230 more ICU beds for coronavirus patients have been added in 33 private hospitals on the directions of the Delhi government.
The number of non-ICU beds in these private facilities has been increased by 842.
The case positivity rate has increased from 1.07 per cent on March 20 to 4.64 per cent on Sunday.
Health Minister Satyendar Jain had earlier said that according to the World Health Organisation, the situation is considered under control if the positivity rate remains below 5 per cent for several days.
The number of cumulative cases as of January 1 had stood at over 6.25 lakh and the total fatalities were 10,557.
The number of daily cases had started to come down in February.
On February 26, the month’s highest daily count of 256 cases was recorded.
However, the daily cases began to rise again in March and have been steadily increasing since then.
Health experts and doctors have attributed this “sudden rise” in cases to people turning complacent, not following COVID-appropriate behaviour and “assuming all is well now”.
The next two-three months could be challenging, they said, adding the situation can be kept under control if vaccination is opened up for more people and COVID-19 protocols are strictly adhered to.
Chief Minister Arvind Kejriwal had said on Friday that Delhi is encountering the fourth wave of COVID-19 infection but the imposition of a lockdown is not being considered yet.
If there is a need for a lockdown in the future, a decision will be taken after due public consultation, he had said, adding the fourth wave is less serious than the previous ones as there are fewer deaths and hospitalisations this time.
He had also suggested that the Centre lift the age bar of 45 years for vaccination to pave the way for mass-level inoculation.
If the Centre allowed vaccination at non-healthcare facilities like schools, immunisation be undertaken on a war footing to check the spread of the virus, he had said.