Rotaviruses are classified into multiple serotypes based on their 2 surface proteins:

G (glycoprotein) and P (protease-sensitive protein). These serotypes identify the rotavirus and are significant in eliciting an immune response.⁹

So far, 10 G serotypes and 11 P serotypes have been isolated from humans.³²

G9 strains have now become endemic in the US and have established themselves as the fifth most common serotype worldwide.³³

In Canada, five strains—G1, G2, G3, G4, and G9—are responsible for approximately 95% of rotavirus disease.¹²

In a study of 135 stool samples collected in the metro Toronto/Peel region from November 1997 to June 1998, G serotype was determined by a reverse transcription-polymerase chain reaction (RT-PCR) assay¹²

Adapted from Kostouros E et al¹²

G2 was the second most common serotype found in that study.

In another study, G2 was found to cause more severe disease than other G serotypes.^33,*

* Based on an examination of patient records from the 1995-1996 winter season (December to May), in which information on the patient’s duration and severity of diarrhea, vomiting, and malaise was collected. Symptoms were scored on a severity scale from 2-24. The mean score with G2 strains was 13.0 versus a mean score of 10.0 to 11.0 for G1, G3 and G9.

Variability of Serotypes

The prevalence of particular rotavirus serotypes is highly variable, changing by year and by region. Though G1, G2, G3, and G4 are the most prevalent, there is no way to predict the specific rotavirus serotype to which a person will be exposed. In addition, the immunity acquired from exposure to rotavirus appears to be serotype-specific following initial infection; therefore, multiple serotypes of rotavirus may translate into multiple opportunities for infection.^3,7

Serotype-specific exposure is a reliable predictor of immunity to a particular serotype.⁷