When the first wave of COVID-19 struck India in 2020, the southern state of Kerala emerged as a unique success story in battling the virus. Local authorities promoted the “Kerala model” as a blueprint to contain COVID-19 outbreaks across the country. But now the palm-fringed state of 35 million people has become India’s epicenter for COVID-19 cases.

On September 9, Kerala accounted for 30,193 of the 46,263 infections recorded in India, making up 65% of India’s total caseload. The spike in Kerala comes as India’s total daily COVID cases have plunged from a peak of over 400,000 in the first week of May to around 40,000 cases per day last week.

The Kerala model, which emphasized early mask-wearing and social distancing and was vaunted by local authorities and newspapers last year, isn’t preventing infections as it once did. Health experts say the state may be especially vulnerable to the virus since—unlike other regions—a high share of its population has not yet developed immunity from a COVID-19 infection. Still, the spiraling outbreak also suggests that Kerala’s COVID-19 response may not be as effective as once thought, especially as concerns grow that the state’s high caseload could spill over and trigger another deadly wave of infections across the country.

The Kerala model

Since at least the 1970s, politicians and economists have admired the state of Kerala for its relatively high quality of life indicators despite its low income. Economists have long attributed the state’s success to early investments in health and education, its ability to redistribute income, and high voting rates among citizens.

Today, Kerala continues to punch above its weight, with the highest literacy rate and life expectancy in the country despite having only the ninth-highest GDP among India’s 28 states.

Early in the pandemic, the state pioneered its own response to battle COVID-19, which is now known as the Kerala model.

On Jan. 30, 2020, Kerala recorded India’s first case of COVID-19. Infections began to rise in Kerala and across the country through February and March, but Kerala’s government took a more proactive approach in combating the virus than other states. Kerala closed schools and banned mass gatherings weeks before the central government followed suit, and it deployed thousands of health workers to test, trace, and isolate people who might have been exposed to the virus. Kerala went into complete lockdown days before the central government announced a nationwide lockdown at the end of March.

Kerala’s success carried over to the wave of devastating, Delta variant–driven infections that swept the rest of India this spring and summer.

In late April, as COVID-19 overwhelmed large parts of the country, Kerala staved off the worst of the crisis. At the height of India’s outbreak in April and May, Kerala’s case fatality ratio, which tracks how many people die after getting COVID-19, was 0.5%, lower than the national average of 1.3%. Kerala’s model of widespread mask-wearing, social-distancing, and testing and contact-tracing appeared to be working.

“Unlike other states, the health care system in Kerala was never overwhelmed, and the state always had surplus hospital beds and [supplemental] oxygen,” says Jacob John, a virologist now retired from Christian Medical College.

How it broke

Health experts blame the ongoing resurgence of COVID in Kerala on several factors.

First, Kerala may have simply let down its guard.

Infections began to rise during the 10-day religious festival of Onam, held between Aug. 12 and 23. People mingled with one another, even though the state had banned large group gatherings ahead of the holiday.

Second, Kerala may be a victim of its own success.

Kerala has a high COVID-19 testing rate, meaning that its elevated case numbers may be due to its catching infections that other states with lower testing rates are missing. Kerala’s containment of the first wave also means a higher share of its population is without antibodies and therefore vulnerable to the highly-infective Delta variant, says John.

“If there are two forest fires, which will last longer, the one with more dead trees or less?” asks John.

Third, Kerala’s especially mobile population may be exacerbating the surge.

The state has one of the largest migrant populations in India, with 2.5 million workers from other parts of the country traveling across its borders. An estimated 4 million Kerala residents live and work abroad, mostly in gulf countries like the United Arab Emirates. An estimated 1.2 million or so of the state’s residents have returned to Kerala from overseas since the beginning of the pandemic, raising the risk of imported cases. Dr. Sudhir Kalhan, chairman at the Institute of Minimal Access, Metabolic Bariatric Surgery at New Delhi’s Sir Ganga Ram Hospital, also notes that thousands of medical and paramedical staff recently returned home to Kerala after serving as frontline medical staff in other parts of the country.

Kerala’s population is highly “migratory,” which has likely contributed to the state’s surge in infections, says Kalhan. “Probably, Kerala picked up the virus late during India’s second wave, but the good thing is the cases are plateauing around 30,000 daily,” he says.

Hopes and fears

Political opponents have slammed Kerala Chief Minister Pinarayi Vijayan for failing to protect his citizens in this stage of the pandemic and accused him of promoting the Kerala model as propaganda to gain political support. Vijayan has denied the charges.

The Kerala model for fighting COVID-19 may be on life support. But it isn’t dead.

“Just because [the Kerala model] has not produced results now does not mean that it did not produce results earlier,” says Sandeep Shastri, a political analyst.

In recent weeks, Kerala’s government has ramped up its vaccination campaign, setting up drive-thru vaccination centers and deploying health workers to places like construction sites to inoculate workers.

India’s government reported on September 9 that 58% of the country’s adult population has received a single dose of COVID vaccine and 18% are fully vaccinated. Kerala reports that it has surged ahead of the nationwide drive, with 63% of adults receiving at least one dose of the vaccine and 38% of people fully vaccinated.

Kerala’s COVID-19 deaths, meanwhile, make up nearly half of India’s daily total. The high death rate may, in part, reflect the fact that Kerala has India’s oldest population.

Kerala’s ability to limit deaths may improve as more people get vaccinated. Kerala’s health department said on September 9 that 90% of people who died in Kerala from COVID-19 from June to September were unvaccinated.

But the real danger of Kerala’s outbreak is that COVID-19 has run rampant despite the Kerala-model efforts to contain the virus. Now, the rest of India needs to remain on high alert so that Kerala’s surge does not spark deadly waves elsewhere, says Amir Ullah Khan, former policy adviser for the Bill and Melinda Gates Foundation.

“If you ask me, there is no cogent explanation [for Kerala’s outbreak],” Khan says. “Is it a new variant we are looking at?”