India Coronavirus Dispatch: The good, the bad and ugly of antibody tests

Not business as usual at CP: At Delhi’s Connaught Place, crowds have made a return but business as usual has not. Most people who visit CP nowadays do so by car. Even outside the only Metro gate that is open, auto drivers complain of getting very commuters daily. Since the number of tourists has gone down, hardly anyone uses autos. Palika Bazar, which would be packed before the pandemic hit is now seeing business decline to a trickle. CP is also the market where the most number of challans are issued daily for violating Covid-19 norms, according to police. With even bigger stores failing to attract customers, posters that read ‘buy 1 get 2 free’ have been put up. Read more here. 

Maharashtra’s oxygen supply takes a hit: Even as the number of oxygen-requiring Covid-19 cases rose in Maharashtra, many medical facilities, especially smaller hospitals and nursing homes, repeatedly ran out of oxygen since late August. Oxygen manufacturers say that the demand for medical grade oxygen has more than doubled since the pandemic hit. Oxygen dealers, meanwhile, point towards the crippling lack of supply-chain infrastructure, which results in oxygen not reaching hospitals. This assumes greater significance when seen in the context of the state’s high case-fatality ratio—the number of deaths as a proportion of the number of people reported infected. One Panvel-based doctor says his team spent over 24 hours trying to find an oxygen supply source for critical patients. Read more here. 

In Numbers

Cases surge in Chhattisgarh: In terms of confirmed Covid cases Chhattisgarh crossed the 100,000-mark on Saturday, becoming the 18th state in the country to do so. Cases in the state have grown at the fastest rate in India for month of September, at one point rising by over 6 per cent daily. In the month of September, the state’s total caseload has increased by three times, from about 33,000 to over 102,000. Chhattisgarh, right now, also has the highest reproductive number (R) which measures the number of people infected by an already infected person. This R-value has dropped below 1 nationally and for the five states with the highest caseloads but Chhattisgarh has bucked this trend with an R-value of 1.35. Read more here.

Bengaluru Rural bears the burden: In Karnataka, the positivity rate among asymptomatic as well as symptomatic cases over the last week has been the highest in Bengaluru Rural. Positivity rate among asymptomatic cases in the last seven days in the region stands at 29.7. Bengaluru Urban, on the other hand, which is the largest contributor to the state’s tally with over 200,000 cases, has seen a positivity rate of 13.8. As far as symptomatic cases go, the positivity rate in Bengaluru Rural is at 62.6. Local officials blame a temporary drop in testing numbers for the rise in positivity rate as health workers went on strike and the supply of RAT kits took a hit. Read more here. 

Comment

The good, the bad and the ugly of antibody tests: ICMR’s recent sero-study gave rise to more questions than answers. While a part of this is on account of data suppression and confused reporting, it’s also a result of the scientific context in which antibody tests operate. For a sero-survey to be indicative, it’s important to get the specific population to be studied right. “The closer the study’s population represents the actual population, to which the results are to be applied, the better,” says the columnist. Secondly, Covid-19 antibody tests themselves are not very accurate. False positives — though rare — have been known to occur. Also, given our limited understanding of the immunity response to Covid, antibody tests serve better as epidemiological tools rather than as clinical ones. Read more here. 

Understanding Covid-19

Antibody duration: A new study by Max Super Specialty Hospital, Saket, and the CSIR-Institute for Genomics and Integrative Biology has found that antibodies can last longer than 60 days. These results are contrary to another study published recently that showed that antibodies stay for less than 50 days. For the study, 780 people were tested and monitored. The study further showed that 67 per cent of seropositive cases were asymptomatic, implying that antibodies can appear in people without them even realising they have been exposed to the virus. The study also found that seroprevalence among hospital workers saw a hike from 2.3 per cent in April to 50.6 per cent in July. Read more here.