mucus

These mutations lead to thick mucus buildup in the lungs, resulting in chronic infections and long-term lung damage.

She sees many children in her class who she thinks would probably be better off at home: “Kids with a lot of green and yellow mucus. We’ve had kids with active lice in school.”

That virus can transmit through an infected person’s saliva and mucus and likely spreads “when an infected person coughs, sneezes or touches a surface that is then touched by others,” the CDC said.

"It's meant to break up sputum, but kids under two can't spit it out, so the mucus can be aspirated into the lungs, causing pneumonia - yet it is still prescribed."

Open wounds are a danger, and mucus membranes can also be infested, such as inside the nose, according to the CDC.