Rotavirus

From ArticleWorld

Seven major groups of rotaviruses have been identified until now, of which three can infect humans.

Rotaviruses cause vomiting and diarrhea. In fact, they cause most cases of acute diarrhea in children, killing over 500,000 children worldwide every year. Some new vaccines have been developed, however, and will be used as of 2006.

Structure

Rotaviruses have a genome with 11 double-stranded RNA segments, surrounded by a protein capsid with three layers:

• The first layer is formed by the VP2 protein, with each vertex containing a copy of other two proteins, VP1 and VP3.

• The second layer is formed by the VP6 protein.

• The third and outermost layer is formed by the VP7 protein, a structural glycoprotein, and VP4, a spike protein.

The diameter of the particle depends on the type of the virus, but they're generally as big as 100 nm, with a buoyant density of approximately 1.36g/ml in CsCl.

Affections

Rotaviruses can cause acute gastroenteritis, also called infantile diarrhea of stomach flu. The gastroenteritis it causes can vary in severity, from mild to severe. It is characterized by vomiting, low fever and diarrhea and an incubation period of 1-3 days.

The symptoms are caused by an infection of the enterocytes in the villi of the small intestine. This leads to a number of changes in the structure of the epithelium, causing diarrhea and generating the other symptoms as well.

Prevention

In 2006, two vaccines against rotaviruses have been developed and shown to be safe: Rotarix (developed by GlaxoSmithKline) and RotaTeq (developed by Merk). Previous efforts existed and Rotashield, developed by Wyeth-Ayerst, had to be retired because of side effects. The retirement was seen as a bad choice though, because the side effects rarely occurred and would have saved millions in undeveloped countries. Unfortunately, the usage of a vaccine that wasn't marketed in the US because it was unsafe was seen as unacceptable.