A: Rotavirus is the most common cause of severe diarrhea in babies and young children throughout the world. Most children have at least one bout of rotavirus infection by 5 years of age. The illness usually starts with fever and vomiting, followed by watery diarrhea and can last from three to eight days.

Rotavirus is very contagious. The virus is shed in the stool and spreads during diaper changing, touching the child's contaminated hands and touching objects the child has touched such as faucets, towels, food and toys. Symptoms usually appear two days after being exposed to rotavirus.

Although you're probably uncomfortable with your own symptoms of vomiting and diarrhea, babies can get even sicker with rotavirus. If your baby is so sick that she has lost interest in eating and drinking, she could be suffering from dehydration. The essential treatment is to replace her lost body fluids by giving her lots to drink. It's usually best to give babies small amounts of fluids as frequently as possible. Helpful fluids include breast milk (if your wife is still breastfeeding), formula (many doctors recommend changing to soy formula because it can reduce the diarrhea) and special pediatric rehydration solutions containing water, sugar and minerals.

If your baby shows signs of severe dehydration—listlessness, sunken fontanelle (soft spot) on top of the head, sunken eyes, crying without tears, dry mouth and little or no urine in six hours—she needs to be seen in the doctor's office or emergency room right away and may need to receive fluids directly in the vein through an intravenous line. Be sure to call your doctor if you have any concerns that she's not getting better.

To try to prevent the spread of rotavirus in the future, it's important to wash your child's hands and your own hands thoroughly, with soap and water, especially after changing diapers and before preparing food. However, rotavirus has been found to be so contagious, that simple hand washing rarely stops the spread. Now there's a new rotavirus vaccine that has been shown to be highly effective in preventing severe rotavirus infection. Studies have shown that it can prevent about three-quarters of all rotavirus infections, and over 95 percent of severe cases.

The new vaccine, RotaTeq™, is an oral vaccine, a liquid given by mouth rather than a shot. Three doses are needed for good protection, and it's generally recommended that babies get this oral vaccine at 2, 4 and 6 months of age, along with the other shots given at those visits.

For more information on rotavirus and the rotavirus vaccine, visit www.cdc.gov.