As cities around the world go into full lockdowns, an expert says the measures alone are not enough to combat coronavirus.

The World Health Organization's top emergency expert said on Sunday, adding that there need to be public health measures to avoid a resurgence of the virus later on.

"What we really need to focus on is finding those who are sick, those who have the virus, and isolate them, find their contacts and isolate them," Mike Ryan said.

"The danger right now with the lockdowns … if we don't put in place the strong public health measures now, when those movement restrictions and lockdowns are lifted, the danger is the disease will jump back up."