(HealthDay News) -- Chickenpox is caused by a highly contagious virus that's passed from person to person by skin-to-skin contact or through the air.

People infected with the virus may be contagious even before the classic skin rash appears, so preventing its spread can be difficult.

The Maryland Department of Health and Mental Hygiene offers these suggestions to help reduce the spread of chickenpox:

• If you already have symptoms, stay away from others until the blisters have crusted over and dried (typically in about five days).
• After possible exposure to chickenpox, premature babies, people with weak immune systems and pregnant women should get a shot of VZIG (varicella-zoster immune globulin) to help reduce the risk of developing chickenpox.
• Anyone who may have been exposed to the virus and has never had chickenpox should be vaccinated within three to five days.