Gujarat's commercial hub ofAhmedabad continued to remain the worst-hit by coronavirus in the state as it reported 50 fresh cases, the highest-ever in a day, taking the total number of infections to 133, officials said on Thursday.The city, which recorded 50 new COVID-19 cases since Wednesday evening, accounts for a lion's share of the total infections in the state - 133 out of 241 - they said.Out of the 17 persons who have lost their lives to coronavirus in Gujarat till date, 6 were from Ahmedabad, including a 48-year-old patient who died on Thursday morning at SVP Hospital here.The sudden spike in the number of new cases was due to an intensive surveillance being carried out in areas which have been declared as 'hotspots' in Ahmedabad, said principal secretary, health, Jayanti Ravi.According to her, the COVID-19 tally will rise in the days to come as more cases related to the religious gathering in Nizamuddin, Delhi, last month are likely to emerge during the surveillance and the ongoing testing in the walled city area, which has a sizable minority community population.Till now, 11 cases related to the Nizamuddin meet, a key source of the COVID-19 spread in the country, had been reported in Gujarat, all in Ahmedabad, officials had said earlier.Following the discovery of several cases of coronavirus from specific pockets, the Ahmedabad Municipal Corporation has launched a surveillance and sample collection drive since the last few days in areas already under 'cluster quarantine', said civic commissioner Vijay Nehra."Our aim is to maximise screening as well as testing to identify positive cases. As a result of this aggressive drive, we were able to collect 761 samples on April 7 and 886 samples on April 8, much higher than just 20-25 we used to collect a week back."In a way, we are chasing the virus," Nehra told reporters."As a result of this aggressive drive, we were able to detect 50 new cases in one day. If these cases were not detected, the infection could have spread in thousands."The number of cases will increase in the days to come as over 1,000 samples are still pending for examination at the civil hospital's laboratory," he added.Since many cases were reported from the walled city area, a mega drive with the help of 1,900 health workers was launched on Thursday to screen the entire population in the locality, said Nehra.