RELATED STORIES • Viral gastroenteritis • Dehydration

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A child in a child care center develops severe diarrhea. Will the other children get sick, too? It's entirely possible. Despite proper hand washing, viral diarrhea is highly contagious.

Rotavirus is the most common cause of severe diarrhea in infants and children worldwide, according to the Centers for Disease Control and Prevention (CDC). In fact, rotavirus infections are so common that most children have at least one bout with rotavirus by age 2 or 3.

However unpleasant, most rotavirus infections can be treated at home with extra fluids to prevent dehydration. Occasionally, severe dehydration requires intravenous fluids in the hospital. Sadly, dehydration related to rotavirus is a major cause of childhood deaths in developing countries.

Rotavirus infections are most common in the winter and spring. A new vaccine can help prevent rotavirus infections in infants. For older children and adults — who aren't as likely to develop serious signs and symptoms of rotavirus — frequent hand washing is the best line of defense.

A rotavirus infection usually starts with a fever, followed by three or more days of watery diarrhea and vomiting. The infection can cause abdominal pain as well. In adults who are otherwise healthy, a rotavirus infection may cause only mild signs and symptoms — or none at all.

Rotavirus is present in an infected person's stool several days before symptoms appear through up to 10 days after symptoms subside. The virus spreads easily through hand-to-mouth contact throughout this time — even if the infected person doesn't have symptoms.

If you have rotavirus and you don't wash your hands after using the toilet — or your child has rotavirus and you don't wash your hands after changing your child's diaper or helping your child use the toilet — the virus can spread to anything you touch, including food, toys and utensils. If another person touches your unwashed hand or a contaminated object and then touches his or her mouth, an infection may follow.

Sometimes rotavirus spreads through contaminated water or infected respiratory droplets coughed or sneezed into the air.

Because there are many types of rotavirus, it's possible to be infected more than once. However, repeat infections are typically less severe.

Rotavirus infections are most common in children ages 4 months to 24 months — particularly those who spend time in child care settings. Older adults and adults caring for young children have an increased risk of infection as well.

Call your child's doctor if your child:

• Has severe or bloody diarrhea
• Has frequent episodes of vomiting for more than three hours
• Has a temperature of 102 F or higher
• Seems lethargic, irritable or in pain
• Has signs or symptoms of dehydration — dry mouth, crying without tears, little or no urination, unusual sleepiness or unresponsiveness

Call your doctor if you:

• Aren't able to keep liquids down for 24 hours
• Have frequent episodes of vomiting for more than two days
• Vomit blood
• Have blood in your bowel movements
• Have a temperature higher than 101 F
• Have signs or symptoms of dehydration — excessive thirst, dry mouth, little or no urination, severe weakness, dizziness or lightheadedness

Rotavirus is often diagnosed based on symptoms and a physical exam. A stool sample may be analyzed in a lab to confirm the diagnosis.

Severe diarrhea can lead to dehydration, particularly in young children. Left untreated, dehydration can become a life-threatening condition.

There's no specific treatment for a rotavirus infection. To prevent dehydration while the virus runs it course, drink plenty of fluids. If your child has severe diarrhea, offer an oral rehydration fluid such as Pedialyte — especially if the diarrhea lasts longer than a few days. For children, a rehydration fluid can replace lost minerals more effectively than can water or other liquids. Severe dehydration may require intravenous fluids in the hospital.

To reduce the spread of rotavirus, wash your hands thoroughly and often — especially after you use the toilet, change your child's diaper or help your child use the toilet. But even strict hand washing doesn't offer any guarantees.

Enter the rotavirus vaccine. In early 2006, the Food and Drug Administration (FDA) approved a new vaccine (RotaTeq) to prevent rotavirus infections in infants. The vaccine is given by mouth in three doses, often at ages 2 months, 4 months and 6 months. Studies indicate that the vaccine prevents about 74 percent of all rotavirus cases, and about 98 percent of the most severe cases. The vaccine is not approved for use in older children or adults.

In 1998, the FDA approved the first vaccine for rotavirus (RotaShield). But RotaShield was withdrawn from the market in 1999 after reports linked it to an increased risk of intussusception — a rare but life-threatening form of intestinal blockage.

If your baby is sick, offer small amounts of liquid. If you're breast-feeding, let your baby nurse. If your baby drinks formula, offer a small amount of an oral rehydration fluid or regular formula. Don't dilute your baby's formula.

If your older child isn't feeling well, encourage him or her to rest. Offer bland foods, such as soda crackers and toast. Plenty of liquids are important, too, including an oral rehydration fluid. Avoid apple juice, dairy products and sugary foods, which can make a child's diarrhea worse.

If you're struggling with diarrhea or vomiting, take it easy. Suck on ice chips or take small sips of water or clear sodas or broths. Eat bland foods. Avoid anything that may irritate your stomach, including dairy products, fatty or highly seasoned foods, caffeine, alcohol and nicotine.