"The studies clearly show that the risk of transmission in airplanes is low," he said.

This practice increases the risk of transmission from women to men.

Some doctors and other critics called the action excessive given what is believed to be a very low risk of transmission.

Certain medical conditions, like hepatitis C, can also increase the risk of transmission to the baby.

There is a remote risk of transmission by human bite.

They said more research is needed to assess the risk of transmission.

A long labor is associated with a greater risk of transmission.

The study showed a 67 percent reduction in the risk of transmission.