World health officials say the respiratory disease spreads through human-to-human contact, droplets carried through sneezing and coughing as well as germs left on inanimate objects. The coronavirus can go airborne, staying suspended in the air depending on factors such as heat and humidity, they said.

Kerkhove said health officials are aware of several studies in a number of countries looking at the different environmental conditions that COVID-19 can persist. Scientists are specifically looking at how humidity, temperature and ultraviolet lighting affects the disease as well as how long it lives on different surfaces, including steel, she said.

Health officials use the information to make sure WHO’s guidance is appropriate, and “so far … we are confident that the guidance that we have is appropriate,” she added. Health officials recommend medical staff wear so-called N95 masks because they filter out about 95% of all liquid or airborne particles.