India's puzzling Covid contrast: How severity differs from Kerala to Delhi

Kerala is adding more than 20,000 new cases every day, but only 1.2% active cases are admitted to ICUs. In contrast, Delhi, with 50 new daily infections, has 24% critical cases

Daily Covid-19 infections in India fell to a five-month low at the end of July. Average daily infections in Delhi--which saw one of the worst surges--have dipped to 50 in the last week, down from a peak of 25,000 daily infections in April. The national capital is reporting less than 600 active cases. 

However, some states like Kerala are witnessing a surge in Covid-19 infections. Kerala’s seven-day moving average of new cases rose 70 per cent from end-June to end-July, even crossing 23,000 on August 3. Consequently, active cases in the state have crossed 170,000. 

But in terms of the relative severity of the disease, the two states exchange their roles. Here, we define the critical patients ratio as the number of patients in the intensive care unit (ICU) as a proportion of active cases. 

Delhi had a critical patients ratio of 24 per cent at the end of July, compared to Kerala’s 1.2 per cent. This stark variation when it comes to critical patients is puzzling because of three reasons: the two had a similar trajectory of surge in cases during the second wave (2,000 to 20,000 in a month), have comparable testing rates (more than 3,000 per million), and better vaccination speed than the national average (about 40 per cent have received first dose). 

The two states form two ends of the spectrum in terms of severity of the disease in the country. Most other states or cities (for which data is available) fall in between the two. 

Mumbai too had a high critical patients ratio, with 16.3 per cent of active cases in ICU (826 out of 5,082) by July-end. Bengaluru, which also had a tide of rising infections during the second wave, has a lower rate of ICU admissions than Delhi and Mumbai. On July 31, Bengaluru had 8,529 active cases, of which 98 patients (1.1 per cent) were admitted to ICU. 

Pune’s ratio is lower than Mumbai's, but has a higher proportion of critical cases than Bengaluru. On July 31, Pune had 2,548 active cases and 222 people admitted in the ICU (critical patients ratio of 8.7 per cent). Punjab, a state which had an earlier onset of second wave than Delhi and Maharashtra, stood at 3.4 per cent on July 29. 

A simple ratio of ICU capacity to the patients treated in ICUs during the peak clearly shows that severity of the disease was more in places where the critical patients overflew the capacity. 

Delhi has an ICU bed capacity of 3,868, but the number of patients in ICU was 5,744 during the peak. Pune had 1,413 critical patients at peak, and the current ICU capacity is 1,400. While data for Punjab’s peak is not available, ICU patients are likely to have surpassed ICU capacity at peak, if we consider that the ratio of critical cases to patients requiring oxygen remains stable. 

Kerala, on the other hand, still has a capacity of 7,628 ICU beds, much higher than the 3,825 beds it required during the peak of the second wave. 

Apart from this factor that starkly differentiates Kerala from Delhi, they stand close to each other on the three aforementioned factors. 

Similar trajectory

Kerala has the lowest cumulative case fatality rate (CFR) among big states, at 0.5 per cent, or one death per 200 cases. Delhi’s CFR stands at 1.72 per cent, close to Pune city’s 1.8 per cent. Punjab overshoots most states, with CFR at 2.7 per cent to date. The way critical patients ratio changed over time stands testimony to Kerala’s performance of achieving the lowest death rate among peers. 

If we map the critical patients ratio over time, we get even more valuable insights on how Kerala seems to have managed to save lives better.

In the second wave, Delhi went from 1,000 cases a day to 20,000 per day in less than a month, from the fourth week of March to the third week of April 2021. Cases peaked on April 20 in the national capital. Critical patients peaked a month later, towards the end of May. Critical patients ratio, or the number of patients in ICU as a proportion of active cases, peaked another month later, at end-June, and was as high as 33.2 per cent. 

Kerala too went on a similar path, with a higher caseload in absolute terms, but a smaller caseload relative to the population. 

Kerala went from 2,000 cases to 20,000 in about a month, but with a two-week lag compared to Delhi. Cases peaked in the first week of May, critical patients peaked a month later in the first week of June. Critical patients ratio peaked in mid-June, and was as low as 2.6 per cent. 

Even at the peak of severity, Kerala’s critical patients ratio did not go beyond 3 per cent. For Pune city, it peaked at 17 per cent in mid-June, and for Punjab, at close to 11 per cent towards the end of June. 

Comparable testing

Experts feel that timely testing, timely hospital admissions, and the capacity and readiness of critical hospitalisation infrastructure are key reasons states faced the calamity in varying severity. 

“Testing is more prevalent in Kerala in the sense that whoever is in doubt gets tested immediately. Kerala has used rapid diagnostic tests which seem to have helped them,” said Jayaprakash Muliyil, an epidemiologist at the Christian Medical College, Vellore. 

When the curve falls rapidly, as it happened in the case of Delhi, “a lot of people will naturally be sick in the ICU,” he added. This phenomenon pushed up Delhi’s critical patients ratio above 30 per cent two months after the peak of second wave. 

But Delhi and Kerala are not too far apart when it comes to testing. Kerala increased its testing from 1,082 tests per million people during the lean phase, to 4,126 per million on May 1. Keeping it above 3,000 per million till July, the coastal state has further increased it to 4,808 tests per million on August 1. Delhi too has kept testing above 3,000 per million since the waning of the second wave, not too small compared to 5,000-plus per million during the second wave peak. 

Yet, the difference in critical patients ratio between the two is stark.

Rapid vaccination

Vaccination certainly helped in curbing severe cases across the world, as experiences in the UK and the US have demonstrated. Here, the wide variation in disease severity in Delhi and Kerala is puzzling especially since even the vaccination progress in the two has followed nearly the same path. 

While Delhi has given one dose to 38 per cent of its people, Kerala has crossed 41 per cent. Thus, there are other factors that explain the severity variation. 

Epidemiologists point out that apart from testing, having health infrastructure and human resources in place is also a key factor.

“The number, quality and distribution of public health facilities help in efficient prevention and management,” Giridhar R Babu, professor and head – Life Course Epidemiology at Public Health Foundation of India, told Business Standard.

Apart from this, he also reiterated the importance of testing and general awareness among the populace. 

“Early identification and timely referral, including provision of advanced care, help in preventing progression of the disease into severe illness. Awareness of the people regarding early testing, treatment also matters a lot,” he added.