BACKGROUND:
Rotavirus is the leading cause of viral gastroenteritis of infants worldwide, causing deaths estimated at >500,000/yr. An effective vaccine would be invaluable. There is some evidence that immune protection is specific to VP7 (G) serotypes. Serotypes G1-4 are predominate, but emergence of new serotypes may be of public health importance.

OBJECTIVE:
Maintain surveillance of changing patterns of prevalence of rotavirus serotypes in the Philadelphia area annually (since 1994).

METHOD:
All infants admitted to Children's Hospital with symptoms of gastroenteritis during the winter-spring season are tested by ELISA for rotavirus. Serotype, VP7 (G), is determined by RT-PCR, product sequencing and sequence homology. The target sequence of the VP7 gene segment also provides additional knowledge of VP7 sub-types.

RESULT:
Serotypes were determined in 156 of 159 ELISA+ specimens (2003-04) were G1 (66%), G2 (1%), G3 (6%), G4 (10%), G9 (2%) and G12 (10%). Serotype G12 was first identified in Manila in 1987-8 and has been identified throughout Asia. G12 has recently been reported in Argentina, but remains rare in North America. We thus report the first G12 outbreak in North America. The G12 infection season corresponded to that of other rotavirus strains, with no differences in age, sex, racial or geographical distribution.

CONCLUSION:
Preliminary studies of rotavirus strain G12, virtually new to North America, exhibited no epidemiological or demographic characteristics different from traditional strains. Nevertheless, the requirement for G12-specific immunity for protection remains to be determined.

LEARNING OBJECTIVES:
The need for surveillance for rotavirus serotype is necessary to provide a predictor of new strain emergence as a guide for design of vaccine of maximum specific protection against circulating serotypes.