A new drug could save lives by providing effective treatment for the most common cause of childhood diarrhoea.
Virus is devastating in the developing world
Rotavirus kills up to 600,000 children a year in developing countries, and accounts for a third of hospital admissions from diarrhoea worldwide.
US researchers in Florida say a simple drug treatment cuts the duration of the illness by more than half.
Details were published online by The Lancet medical journal.
Symptoms of rotavirus infection include vomiting, fever, abdominal pain, dehydration and watery diarrhoea. In severe cases it can cause dehydrating gastroenteritis, which can be fatal.
The researchers studied 50 children admitted to the Cairo University Children's Hospital last summer with severe infection.
The children were either given the drug nitazoxanide, which is currently only licensed in the US, or a placebo.
No current drugs
The researchers found that the illness cleared up after an average of 31 hours in those treated with nitazoxanide, compared to an average of 75 hours for the placebo group.
Lead researcher Professor Jean-Francois Rossignol, of the Romark Institute for Medical Research in Tampa, said: "Additional clinical trials are being done in larger numbers of patients to confirm our results.
"In the interim, the results reported here are encouraging and might lead us to think about new approaches to managing rotavirus disease in children."
Professor Tony Hart, from the University of Liverpool, said it was surprising, but welcome that the drug was effective against rotavirus, as it had been initially developed to tackle another type of organism, a protozoan.
He said: "Anything that can ameliorate the effects of rotavirus would be very good, as we have not had any drugs that work at all against it until now."
However, Professor Hart warned that access to a new drug might be problematical in the developing world.
He said it was vital that children who developed rotavirus diarrhoea were kept hydrated.
The introduction of rehydration salts 20 years ago had had a significant impact, he said, but again there were problems with access in developing countries, where there was also no guarantee of clean water to prepare them for use.
Vaccines in development
Vaccines against the virus are also currently being developed. A study published by the New England Journal of Medicine in January reported promising results from tests of two vaccines - Rotateq and Rotarix - involving 130,000 children.
The studies found them to be 98% and 85% effective respectively, it said.
In the UK, it is estimated that 1 in 38 children will be hospitalised for rotavirus gastroenteritis by the age of five, and that each year 14 children under five will die.
Most infections occur in children under two.
It is so devastating to children in the developing world because of the lack of prompt access to treatment and hospital care.
The quest for a safe and effective vaccine against the virus was thought to be over in the late 90s when a previous vaccine was developed.
But that had to be withdrawn from the market after it was associated with an uncommon, but potentially life-threatening condition called intussusception, where the bowel folds in on itself, causing an intestinal blockage.