Telangana’s Directorate of Public Health had stated last month that they have observed transmission of the virus in “communities”. But this is not the same as “community transmission” as technically defined by the World Health Organisation (WHO).

WHO differentiates between “community” and “local transmission”. A country/ region is said to be in the stage of community transmission if there is inability to relate confirmed cases through chains of transmission for a large number of cases or by increased positive tests through sample testing, explained Indian Institute of Public Health (IIPH)-Hyderabad director G.V.S. Murthy.

Chain mostly discernible

For most cases in Telangana, the transmission chain is discernible and it is only in a smaller proportion of cases that the contact for transmission is unclear. Many cases have been traced to ‘super-spreading parties’.

However, whether “local transmission or community transmission”, intensity of action will have to be maintained by the State irrespective of the phase of transmission, he said.

The public health expert said a recent study from San Francisco observed that 71% of the transmission occurs in households, 17% in neighbourhood and 12% in the workplace. Masks reduce effective transmission by 8.6%., US statistical analysis showed that countries following recommendation of limiting gatherings to ≤10 people lowered the growth rate of COVID-19 significantly more as compared to counties which did not implement the guideline.

Data from 149 countries showed that the incidence of COVID-19 decreased by an average of 13% in association with physical distancing interventions. No evidence was found of additional benefits from closure of public transport when four other physical distancing measures — school closures, workplace closures, restrictions on mass gatherings, and lockdown were in place. Earlier implementation of lockdown was associated with a larger reduction in the incidence of COVID-19, said Dr. Murthy.

In the UK, models using data from more than 40,000 people estimated that combined isolation and tracing strategies would reduce transmission more than mass testing or self-isolation alone. Mass random testing of 5% of the population each week will lead to 2% transmission reduction.

Self-isolation alone of symptomatic cases within the household will lead to a 29% transmission reduction. This increased to 35% for self-isolation alone outside the household, 37% for self-isolation plus household quarantine, 64% for self-isolation and household quarantine with the addition of manual contact tracing of all contacts; 57% with the addition of manual tracing of acquaintances.

In Brazil, a social isolation index was calculated and it was seen that on average, every 10% increase in the isolation index was associated with 26% fewer cases of COVID-19 and 18% fewer deaths. Another study observed that, if 80% of the population wears a moderately effective mask, nearly half of the projected deaths over the next two months could be prevented in the US.

Other studies also show that use of face masks by the general public is potentially of high value in curtailing community transmission. Greatest benefits are when face masks are used in conjunction with other practices like social distancing and when adoption is nearly universal and compliance is high. This shows how beneficial conventional wisdom can control the pandemic, he added.