NEW DELHI: In the biggest spike in coronavirus infection on a single day, India on Friday recorded 1,752 fresh cases taking the total number of infected people to 23,452 even as doubling rate of the disease improved to 10 days from 7.5 reported earlier this week, according to the health ministry.The death toll from the infection rose to 723 with 37 fatalities reported since Thursday evening, said an official, adding about 20.52 per cent of the infected people have recovered so far.At a daily media briefing, Director of National Centre for Disease Control S K Singh said around 9.45 lakh suspected coronavirus cases have been under surveillance and their samples are being collected upon detection of symptoms of the infection.Niti Ayog member V K Paul, chairman of an empowered group on Covid-19, said India would have recorded around one lakh cases of the infection by now if Prime Minister Narendra Modi had not taken the "timely step" step of enforcing a nationwide lockdown from March 25.The officials said the outbreak of the pandemic has been "under control" in India largely due to a robust surveillance network along with implementation of the lockdown and other containment measures.Out of the total 1,752 new cases, Maharashtra reported the highest number of 778 new infections followed by Gujarat with 217 cases and Madhya Pradesh with 157 cases, according to government data.The previous highest single day increase of the infection was on April 20 when 1,540 cases were reported. India's first coronavirus case was reported on January 30.Paul said the lockdown has been effective in slowing down the rate of spread of the deadly infection and that the doubling rate now stands at 10 days."No need to fear about hidden spike in cases, The disease is under control," he said.On April 20, the health ministry said the doubling rate has improved to 7.5 days as against 3.4 days before the nationwide lockdown was imposed."If we go back to March 21, the cases were doubling in around three days. An important turn came on March 23 after the janata curfew had happened. The direction changed and the doubling rate increased to five days," Paul said."By then, we had already put in place travel restrictions and had created an environment of social distancing. There were some disturbances in between which led to some setbacks. But from April 6 again, the doubling time started improving," he said.The official said the growth curve of the infection has begun to flatten. "The nationwide lockdown helped take us away from the exponential growth curve and, thereby, contain the growth of coronavirus cases," he said.Officials, however, said these projections are based on the growth pattern at a particular time.Paul also credited the testing strategy adopted by India saying volume of testing has been adequate. Despite there being an increase in testing, proportion of positive cases have not risen.Singh said that surveillance has been the country's primary weapon in the fight against novel coronavirus."We started our surveillance mechanism even before the first case was reported in India. This played an important role in helping us contain the spread of the infection," Singh said explaining how the government initiates contact tracing once a person is found infected in a community."Starting from stopping of international flights to stop transmission of infection from abroad, graded steps including lockdown were taken to halt internal chain of transmission of the infection," he said.Singh said the surveillance network has been set up at district level as well so that measures like household survey, quarantine and isolations are carried out as part of the cluster containment plan."During initial period of lockdown, doubling time of cases decreased since people infected already were being detected, later it improved as lockdown put a brake on the spread of the infection," Singh said.According to Paul, surveillance has been a great tool in containing coronavirus infection cases. Besides containing spread, augmenting testing, improving preparedness, the nation has brought about a massive behaviour change through a Jan Andolan, he said.Joint Secretary in the health ministry Lav Agarwal said that 15 districts in the country which earlier reported cases of the infection have not reported any fresh cases in the last 28 days.Further, a total of 80 districts from 23 states and union territories have not reported any new cases since the last 14 days.Talking about the feedback of the central teams which visited various states witnessing higher growth in positive cases, Agarwal said the teams took stock of the hospital settings, examined the containment plans around containment zones and discussed with states over strengthening the contact tracing system.They had some observations which included increasing the mobility of the teams, deploying additional teams in area of containment zones for active house-to house survey.They also examined how the clinical management of admitted patients can be strengthend.The teams also highlighted that the healthcare workers and volunteers like NCC as well as retired professionals should be trained on prevention of the infection.Agarwal also said that Union health minister Harsh Vardhan interacted with all the state health ministers and health secretaries through a video conference to review the preparedness and actions taken for management of COVID-19 on Friday."He also asked them to focus on surveillance, house-to-house active case finding, early identification of cases and proper clinical management to ensure that the patients get timely treatment and mortality is reduced," Agarwal said."He urged the health ministers to personally review the measures being undertaken against stigma and discrimination of doctors and other frontline health workers, as also patients who have Covid-19 or those that have recovered," he added.Officials said the number of active Covid-19 cases in the country stood at 17,915 as 4,813 people recovered from the infection.About 20.52 per cent of the cases have recovered so far, a health ministry official said.