In cities at least, India’s nightmarish second wave of COVID-19 finally seems to be ebbing. Delhi has brought its test positivity rate below 2% for the first time in two months.

The pandemic’s scars won’t be easily erased, however — and they should be a warning to other developing nations. Those countries must learn from India’s experience if they don’t want to repeat it.

The first and most obvious lesson is to avoid overconfidence. A relatively small change in how transmissible the novel coronavirus is can have large, nonlinear effects on how fast it spreads. That means strategies that kept the pandemic at bay in 2020 won’t necessarily work in 2021. As new variants emerge, health authorities might need to lock down more firmly and in a more targeted fashion to remain safe.