The six-foot separation recommendation may not be sufficient in preventing the spread of coronavirus, says a Massachusetts Institute of Technology professor.

Local and federal officials have asked residents to practice social distancing and stay six feet away from other people.

But Lydia Bourouiba, an associate professor at MIT who studies the interface of fluid dynamics and epidemiology, published an article in the Journal of the American Medical Association last week arguing that the six-foot separation recommendation is based on potentially outdated research.

The model for respiratory disease transmission used by organizations like the World Health Organization and the Centers for Disease Control and Prevention is from the 1930s, according to Bourouiba.

New research shows that respiratory disease transmission is also dependent on environmental factors like temperature and humidity, says Bourouiba. So, the recommendation to maintain six-feet away from other people may reflect an underestimation of how far COVID-19 droplets can travel.

Because it is unclear how far COVID-19 can travel, Bourouiba says its crucial that health care workers use personal protective equipment when caring for patients with coronavirus. But PPE shortages continue to be a problem for health care workers.