Rotavirus is the most important cause of diarrhea in Japan among young children, with the prevalence ranging from approximately 9.7 to 88%.  Rotavirus is also the leading cause of acute viral gastroenteritis in young children worldwide and is associated significantly with infant mortality rates especially in developing countries.

The four most common types are G1 to G4 but since 1994, a new type called G9 has emerged in young children.  G9 rotavirus belonging to 2 different subtypes is particularly prevalent in Japan and G9 has recently become the most prevalent strain in several other countries. G1 is predominant in children, but the G9 strain has recently been found to be dominant in adults at a rate higher than for children.  (A Swedish study showed two out of four samples from children and three out of six samples from adults were G9.) There is evidence that the elderly are particularly susceptible. Thus, if you have a case of G9 rotavirus infection at home, it would be prudent to try to prevent contamination spread to other members in the household.

It is clearly seasonal in Japan, with a peak of rotavirus activity in late winter (February) through early spring (March). The infection is predominant among children aged 1-2 years of age, although also common in children of 2-3 years.  There is an oral vaccine called Rotarix that is available in Japan. 

To know more about the sickness, read on … the following information on Rotovirus is excerpted from the article Siblings felled by dreadful virus (retr. HealthXchange.com):

Dr Nancy Tan, a consultant paediatrician at Singapore Baby & Child Clinic, said that nearly every child will have at least one episode of rotavirus-related diarrhoea by the age of five. However, children above five can also fall ill and they sometimes end up sicker although it is not clear why, she said.

The rotavirus is transmitted between persons, through eating and drinking contaminated food or water, or by touching contaminated surfaces like toys, so it is not unusual to see siblings catching it at the same time.
It is a hardy virus which can survive for hours on hands, for days on solid surfaces and up to a week in human faeces, said Dr Tan.

Transmission can be greatly reduced by good hygiene, namely washing hands frequently, especially after going to the toilet. Rotavirus sometimes causes death because of dehydration, as a patient could have up to 20
bowel movements a day. While the infection subsides after about a week, the diarrhoea can persist for up to three
weeks, she said.

It is not known how prevalent the virus is but the KK Women’s and Children’s Hospital sees some 600 rotavirus-related admissions a year, said Professor Phua Kong Boo, a senior consultant of its gastroenterology service. Three quarters of those children are under five.  

The Health Ministry said that no child here has died of the virus. But parents who want to take precautions can have them immunised against it. The vaccination is not included in the list of compulsory childhood vaccines. It costs between $180 and $220 and should be given by the time the child is eight months old. Parents should clean contaminated play area surfaces and toys with hydrogen peroxide, bleach or alcohol rub to destroy the virus and prevent transmission. – End of article excerpt

While few actually die from the sickness, the dangers are mostly from dehydration and it can be fairly debilitating while it lasts or burdensome if the parent caring for the child is also suffering from the rotavirus as well. With severe cases of rotavirus, complications of dehydration can develop when the usual at-home diarrhea treatments of clear fluids, BRAT diet may not work because of persistent vomiting and diarrhea, so medical hospitalization with intravenous drip may be required.

A.K.

References:

Rotavirus infection in children in JapanPediatr Int. 2000 Aug;42(4):428-39. PMID: 10986883 [PubMed – indexed for MEDLINE]