The US logged 125,735 new COVID-19 cases on Monday, according to the CDC's tracker. India, a country whose population is more than four times bigger than our own, logged ... 11,000. Their current case-per-capita rate is about 9 in 1 million, one of the lowest on the planet, reports Business Insider. Why is one big mystery, reports NPR, which notes that as recently as September, India was seeing nearly 100,000 cases a day and was gunning to surpass the US' caseload count. What in the world changed? That's what scientists are trying to figure out. Jishnu Das, a health economist at Georgetown University, says the drop isn't due to a decrease in testing or reporting, and the drop began before any vaccines were approved. NPR looks at possible factors at play. One is age. As of 2016, 15.2% of Americans were over age 65; the corresponding figure in India is 6%. That younger population could mean that more people who get COVID aren't showing symptoms.
Another is mask wearing. The country has mandated that masks be worn in public spaces; in Mumbai, for instance, that applies even to those outdoors, like runners. Those who don't comply are fined. The country's warm and humid climate may also be a contributing factor, with some research indicating that in those conditions droplets of the virus don't stay suspended in the air as long. One more theory: That Indians are benefitting from more robust immune systems created by the prevalence of diseases like malaria and typhoid, and are experiencing milder cases as a result. Indeed, Fortune reports that a January survey of blood samples taken in Delhi found 56% had coronavirus antibodies. The case count there is 635,000, but that figure suggests the true number of infections could be closer to 10 million and potentially putting the city close to achieving herd immunity. (Read more coronavirus stories.)