New Delhi: India's top health research body has said it was not clear about the extent to which Covid 19 would spread in the country.According to an analysis by the Indian Council of Medical Research ( ICMR ), even if symptomatic cases are comprehensively identified and quarantined, the delay in Covid-19 reaching epidemic levels within India would be days and not weeks.At this point, it is difficult to predict the number of beds required or ventilators necessary to treat Covid-19 patients, it said.ICMR has developed a mathematical model to study the transmission dynamics as Covid-19 has started spreading in India. The analysis is based on the data from four most populated metropolitan areas (Delhi, Mumbai, Kolkata and Bengaluru), as well as their population connectivity."We chose to focus on these population centres on the assumption that the introduction of Covid-19 was most likely to occur in international transportation hubs, and thus that these cities were most likely to be the focal points of initial Covid-19 transmission in the country," it said.According to the data, if symptomatic arrivals alone were screened, the model projections for the time to epidemic ranged from 45 to 47.7 days. Additional detection of 90% asymptomatic individuals would delay the average time to epidemic by 20 days, it revealed.As per the study, where 50% of symptomatic cases are quarantined (whether voluntarily or through screening and testing) within an average of three days of developing symptoms, such measures could reduce peak prevalence substantially, minimising pressure on public health services.As a consequence, the intervention has the effect of "flattening" the epidemic curve, distributing cases over a longer duration than in the absence of intervention.In an "optimistic" scenario, quarantining 50% of symptomatic cases within three days of developing symptoms would reduce the cumulative incidence by 62% and the peak prevalence by 89%.In a closed setting of similar nature as that on the cruise ship 'Diamond Princess', the experts expected 26% of the population to get infected and one in 450 infected individuals to die."We deduce that around 5% of the infected patients will require intensive care and half of those admitted in the intensive care unit will require mechanical ventilation," it said.