Positivity rate rising, points to faster spread

NEW DELHI: The average rate of samples testing positive for Covid-19 across the country has risen from 4.6% for the week ending May 17 to 7.8% for the week ending June 17, but the rise has been alarming in states such as Delhi and Haryana — a trend experts said is suggestive of an expanding outbreak.

In Delhi, the figure has grown from 7% on May 17 to 31.6% on June 17, according to government data analysed by HT. In other words, while seven of every 100 samples were turning out to be positive a month ago, this has risen to 31 of 100 now.

India does not give out data of individuals tested but of samples tested. This means that people who get tested multiple times are counted every time, so the positivity rate may be higher than what data suggests.

More than 6.2 million samples have been tested for Covid-19 in India as of June 17, of which 367,117 cases have been reported, resulting in an overall positivity rate of 5.9% from when testing began in January.

The rise of positivity rate, coupled with increasing new cases, suggests that the virus is spreading in the community, experts said.

“An increase in positivity rate is a reflection of the increase in prevalence of the virus in the community,” said T Jacob John, former head, Indian Council for Medical Research’s Centre for Advanced Research in Virology.

A rising positivity rate can be heavily influenced by targeted strategies -- such as the one in India, where only those exhibiting symptoms are tested. The downside of this is that large sections of population who are asymptomatic are left out.

“We have tested less than 0.5% of the total population in the country; this is a very small number. We can’t assume that the entire infected population is confined to a tiny fraction. The rising positivity rate indicates that infection rate is increasing in the remaining 99.5% and indirectly points to the fact that there is community transmission happening,” John said.

Among the 10 worst-hit states, Delhi reported the biggest change in positivity rate (from 7% on May 17 to 31% on June 17), followed by Haryana (1% to 10.1%) and Tamil Nadu (4.2% to 10%).

The positivity rate has increased from 16.4% on May 17 to 21.2% on June 17 in Maharashtra, the state with the highest number of cases and deaths.

Gujarat, Rajasthan and Madhya Pradesh, however, are the only states among the 10 worst-hit regions to report a reduced positivity rate -- albeit marginally. In Gujarat, it went from 11.3% to 10.1%, in Rajasthan from 2.2% to 2% and in Madhya Pradesh from 4.3% to 2.8%.

IN DELHI, THE FIGURE

HAS GROWN FROM 7% ON MAY 17 TO 31.6% ON JUNE 17, WHICH MEANS 31 OUT OF EVERY 100 PEOPLE ARE TESTING POSITIVE IN THE CAPITAL