The average positivity rate — the proportion of tests that return positive for Covid-19 — in the state also underlines the worrying situation. On average, 19.7% samples tested in the state have returned positive for Sars-CoV-2 in the past week. This number is nearly four times the threshold of 5% recommended by the World Health Organization (WHO) in order to establish if a region is testing adequately and has the outbreak under control. This number, which is a crucial statistic that shows how prevalent the virus is in society, is still rising. A rising positivity rate in a region, when coupled with increasing new cases, indicates that the virus is spreading fast within the community.

The testing gap

To arrest the magnitude of the transmission owing to the presence of new variants, the state went into a lockdown starting May 10 which will go on until May 24. However, during this period, new cases and deaths have continued to rise but testing has remained the same. An average of 158,000 tests per day were conducted in the past week.

Experts say that Tamil Nadu needs to double its testing. “We aren’t testing adequately but it is a challenge to scale up RT-PCR tests,” says Dr Prabhdeep Kaur, deputy director, National Institute of Epidemiology.

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As a policy, Tamil Nadu only follows RT-PCR testing — the gold standard to detect the novel coronavirus. “But now is the time to consider adding rapid antigen tests,” says Kaur. “RT-PCR testing labs are stretched out and if turnaround time for results is late, it defeats the purpose.” With 267 labs (198 private and 69 government labs), the state already has one of the highest number of labs approved for Covid-19 labs.

“We have the capacity to test 300,000 samples a day,” says health secretary J Radhakrishnan. During the first wave, the state’s thumb rule was to test a minimum of 10 people for every positive case. That’s how experts have arrived at a figure of conducting 300,000 tests daily as the average of new cases reported daily in the past week is 31,137. This is a rapid increase from 17,865 average daily cases between April 26 up to May 2 — the day of election counting in the state. The following week, the average daily cases went up to 24,735.

Testing also varies district-wise depending on the number of infections as well as lab facilities. Chennai accounts for 27% of the cases in the state which is the highest among the 37 districts.

“But we need to worry more where there are less cases also,” says Kaur. “If you see the pattern of the virus transmission in the second wave such as in Maharashtra and UP, there was rapid transmission in smaller districts also while we saw only a majority of cities being affected in the first wave. The lockdown has bought us time, and we have to assess our capacity in smaller districts. Epidemiologically speaking, the virus spreads faster among those who haven’t been infected and vaccinated already. So sero prevalence surveys have indicated that half of Chennai is already infected so people in other districts and rural areas are more susceptible now.” She added that the government setting up buses with oxygen concentrators and oxygen support is a good move to stabilise them until they receive beds.

The pressure on health infra

The state’s key concern is to procure more oxygen and increase oxygenated beds. As of 3pm on May 19, in Chennai’s five government hospitals, there were no ICU beds available and only 49 oxygen supported beds that are vacant. The city’s private hospitals too didn’t have a single ICU bed available. Like elsewhere in the country, patients have been waiting for long hours outside hospitals and being treated inside ambulances before an oxygen supported bed becomes vacant.

After repeatedly appealing to the Centre, Tamil Nadu has been receiving an allocation of 519 MTs of oxygen from the Centre’s pool daily. Additionally, the state has imported 80 MTs of oxygen from the Netherlands and procured 12 cryogenic containers from China.

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“Our own production is limited so we are trying every small avenue to meet the oxygen demand. We want to have a seamless operation so we are focussing on getting most of our oxygen from the east like Rourkela, Durgapur, Telangana, Jameshedpur etc,” says Thangam Tennarasu, minister for industries. They estimate the oxygen demand to shoot up to 800 MTS per day in the coming days.

Due to shortage in vaccines, the Tamil Nadu government officially opens up vaccination for the 18-45 age category on Thursday. So far, the state has vaccinated seven million people. The state has also gone for a global tender for 35 million doses of Covid-19 vaccines.

But for now, the rise in cases, the high positivity rate, inadequate testing, an overwhelmed medical infrastructure, and a much slower than desirable rate of vaccination mean that Tamil Nadu could well decide the next phase of India’s Covid trajectory.