There are 70 million refugees, displaced people and asylum seekers around the world. Close living quarters, significant underlying health problems and limited access to sanitation and medical care mean that COVID-19 — which has no known treatment and has brought some of the best health systems in the world to their knees — poses an outsized threat to these communities. 

Although there are some reports of refugees testing positive for the virus, as of mid-April, there are no known COVID-19 outbreaks in major refugee camps, according to advocates and responders contacted by Nature. But many aid groups fear that it is only a matter of time before the disease strikes. According to advocacy groups, host nations have been slow to enforce preventative measures. And experts fear that aid organizations will struggle to rally and respond.