COVID-19 cases have increased the burden on Delhi's hospitals with the number of vacant beds shrinking fast and out patient departments (OPDs) witnessing a spike in footfall, doctors said on Saturday.Besides, the ICU beds with ventilators at most top private hospitals and major Centre-run facilities are also getting filled up with spiralling cases in the last few days.Delhi recorded over 7,000 COVID-19 cases for the first time, taking tally to over 4.23 lakh on Friday, while the toll rose to 6,833 with 64 more deaths, authorities said.The 7,178 fresh cases came out of the 58,860 tests conducted on Thursday, while the positivity rate stood at 12.19 per cent amid the festive season and rising air pollution in the city, according to the.