Editor’s note: The Economist is making some of its most important coverage of the covid-19 pandemic freely available to readers of The Economist Today, our daily newsletter. To receive it, register here. For more coverage, see our coronavirus hub

INSTAGRAM IS KNOWN mainly for stylish selfies and FOMO-inducing travel pictures. Could the photo-sharing service also be used to track the spread of a pandemic? As governments and health-care providers around the world seek out suspected carriers of the new coronavirus, the popular social network—which people use to share pictures and videos of places they visit, and more generally to socialise—could prove valuable for tracing the path of the virus.

The social-media platform may seem an odd tool for studying the coronavirus outbreak. It is older people, after all, who are most vulnerable to the virus; most Instagram users are under 35 years old. But young people can be powerful carriers of the illness. Because they often experience mild symptoms, infected youngsters may not know they are ill. If they are gregarious and eager to travel, as Instagram users often are, they are even more likely to spread the disease. Even if globe-trotting Instagram influencers self-quarantine after learning of their illness, their travels from a virus hot-spot may have infected people along the way.

To investigate how the social network might be used to track the pandemic, The Economist identified more than 20,000 Instagram users who posted to the platform in cities and towns which at the time had at least 50 confirmed covid-19 cases. We then recorded where these users travelled to after visiting these hotspots, based on subsequent posts in which they tagged their locations, such as a city, town or restaurant. We surmise that, although by no means all of these users were infected with the virus, they were nevertheless potential carriers of it, and thus of interest to those trying to track the disease.

The resulting database included some 64,000 Instagram posts. But not all of them were relevant to our analysis. Some users tagged Wuhan, the likely source of the outbreak, in solidarity with those quarantined there, even when they were located elsewhere. To reduce the number of inaccurate locations, we discarded users traced to Wuhan, as well as those which mentioned “coronavirus”, “covid19”, “epidemic”, “pandemic” or variations thereof. We also omitted posts marked “latergram” or “tbt” (an indication that the photo or video was old). We were left with around 53,000 observations, published in over 2,000 cities across 125 countries.

We found that the movements of Instagram users identified as potential carriers of the coronavirus tended to track the movement of the virus itself, as revealed by case locations published by official sources. Some users travelled to virus-free places that were subsequently hit with an outbreak, raising the possibility that they brought the virus there themselves. Other Instagrammers in our sample offered clues about possible paths of transmission, such as a trip home from a holiday at a Swiss ski resort.

As public-health officials scramble to try to curb the spread of the new coronavirus, having access to accurate, real-time data on the movement of people who might be infected could prove life-saving. Instagram and other social-media platforms offer a steady source of information that could be useful in mapping the pandemic—and perhaps limiting its transmission.

Dig deeper:

For our latest coverage of the covid-19 pandemic, register for The Economist Today, our daily newsletter, or visit our coronavirus hub