A second wave of Covid-19, as China’s and South Korea’s cases have shown, now looks inescapable, if not outright inevitable, for most countries that are looking to end their lockdowns.

A second wave of Covid-19, as China’s and South Korea’s cases have shown, now looks inescapable, if not outright inevitable, for most countries that are looking to end their lockdowns. China’s infection-rates are still quite low, but the country is taking no chances. It has reportedly tested thousands (preemptive testing) over the past few days, while it is looking at shutting down another city where the most number of cases have been detected—bear in mind, the authoritarian Chinese state had enforced total lockdown the first time round, though late in the day.

Tackling a second wave will rely on all the information countries have gleaned from the first round of the outbreak. To that end, researchers, as Nature reports, will be using genome sequencing to prevent, or curb a second wave.

Scientists have so far sequenced 34,000 genomes for the virus globally. This data is expected to help researchers trace “the origin of the outbreak in their countries”. Genomic profiling, studies show, help reduce the duration of outbreaks, and their intensity, by aiding contact tracing.

At the start of a second wave, when there are few cases, available genomic data can be used to spot which clade of the virus one is dealing with, and what was its last geographic trace. New Zealand, which has managed to keep new infections to zero, has sequenced the genome of all variants of the virus from infections within its borders.

Mapping sequences from new infection against the database, researchers can quickly point to links, or lack thereof, between cases—present, and historical. This is useful because, with links established, a wider screening for the virus can be made with precision. But, the wealth of information will depend on how many cases were caught the first time round, and key to this will be a testing strategy that ensures cases don’t go unreported.