Kerala earned global recognition when its government devised an ingenious, low-cost, hands-on approach to tackle the coronavirus outbreak.
Now, the southern Indian state faces an even bigger challenge as thousands of returning citizens threaten to spark a second wave of Covid-19 cases.
The state of 33 million acted quickly to halt community transmission, recording only 524 and four deaths over the past four months.
It recorded India’s first case on January 30, when a medical student returned from virus-hit Wuhan.
Surveillance squads made up of volunteers, district officials and local police and daily random phone calls kept 175,000 people inside their homes obeying strict quarantine rules during a peak in cases in April.
But a resumption of international flights last week and people crossing the border via road has triggered a fresh bout, with at least three imported cases.
"We have been getting our Covid-19 care centres ready because we knew people would be coming [home] from overseas, just like we got ready in January for students arriving from Wuhan," senior official Dr Amar Fettle, who oversees public health emergencies, told The National.
The state faces the prospect of about 450,000 Keralites returning home in the coming months, including many from the Gulf.
Although testing was put in place in many of the countries they are departing from, including the UAE, the nature of the virus makes it difficult to catch those without symptoms.
Ambulances are waiting on the tarmac to take passengers with any symptoms directly to government hospitals.
Batches of 20 are allowed to disembark at a time to keep crowds at immigration and baggage retrieval at a minimum.
All passengers except for the elderly and pregnant women are taken to government quarantine centres.
“We have made plans for every single action starting with announcements about the new disembarking system 45 minutes before the aircraft lands,” Dr Fettle said.
The measures will require diligence and patience in densely populated India.
Across the country, more than 75,000 cases have been reported with 2,440 deaths and 24,900 recoveries.
Kerala had the country's highest infections when a nationwide lockdown began on March 25, and was the first to report no new cases on May 1.
Doctors fixed leaks in handling the coronavirus outbreak as soon as they found that asymptomatic travellers from overseas had spread the disease to family and friends.
Transporting passengers directly to isolation centres began in March, coupled with widespread testing even of asymptomatic travellers and tracing all high-risk contacts.
“We anticipated an inherent resistance to government directives because at that time corona was something distant, it happened abroad and not in India,” Dr Fettle said.
“So we made sure strict quarantine rules were followed. Kerala has the largest number of contacts traced for each single person. At one point we had more than 175,000 people in quarantine.”
Community vigilance was drilled in with a "Break the chain" campaign.
“For public anywhere in the world you can’t only have a velvet glove, you need a stick too. We have citizen volunteers working with police to monitor cases in homes," Dr Fettle said.
"We would give them surprise calls to be sure they stayed home.
“In a media blitz we kept hammering in that it was to save 'your own life and for your own family’s security.' This was not to save Kerala, India, the world or the universe.”
More than 200 passengers on a Dubai-bound Emirates flight were offloaded in March after officials were alerted about a British tourist who did not disclose he had tested positive.
The tourist and 19 companions had broken out of quarantine in a hill resort but were moved to a government facility and the flight was permitted to take off.
Apart from early detection, social support has been key in a state with three million migrant workers.
Shelters were built and community kitchens readied to prepare meals during the 50-day lockdown.
“You can have strict rules like making face masks compulsory but it has to be a people’s campaign,” he said.
“You need to empower, motivate and boost the public’s morale to encourage participation.”
Information about each household is collected by more than 26,000 Asha – accredited social health activist – workers.
This feeds into a primary healthcare system with a network of junior health inspectors, district officials and doctors.
“Literally speaking, no house is left unnoticed,” said Dr Sachin K C, who manages a Covid-19 control room in Kannur district.
“Any house you pick is designated to an Asha worker in the field who reports to the medical officer at the healthcare centre. This surveillance system is in place throughout Kerala and in an epidemic, we just made the network stronger.”
“Even if there is a small symptom in contact cases, the person is taken for testing.”
The state has begun easing measures to allow shops and businesses to open only in areas cleared as green zones, where there is a drop in daily new cases and a rise in patients discharged.
Only 32 patients are being treated in hospital, with 31,143 under home isolation and 473 admitted in isolation centres.
But with more than 400,000 non-resident Keralites registering their intent to return, the numbers are set to rise.
“Going forward, we have challenges not just from the air passengers but interstate road travellers and people may again show a scant disregard for rules and that is a big headache,” Dr Fettle said.
“But we are anticipating this. The lockdown will be relaxed very gradually in stages. We have told people if they are not responsible, we will clamp down again.”