Molecular and epidemiological features of gastroenteritis outbreaks involving genogroup I norovirus in Victoria, Australia, 2002-2010.

GI noroviruses are relatively rare and systematic studies of the molecular epidemiology of GI norovirus outbreaks are lacking. The current study examined the molecular virology of GI norovirus outbreaks in Victoria, Australia (2002-2010). Of 1,617 norovirus outbreaks identified, 69 (4.3%) were associated with GI norovirus alone, 1,540 (95.2%) with GII norovirus alone and 8 (0.5%) with GI + GII. Some differences between GI and GII outbreak epidemiology were found. GI outbreaks peaked in the 2-month period November/December whereas GII outbreaks peaked in the 2-month period September/October and GI norovirus outbreaks were significantly more common in non-healthcare settings (37.7%) than GII outbreaks (9.5%). ORF 1/ORF 2 genotypes found in the 69 outbreaks involving GI norovirus alone were: GI.2/GI.2, 7 outbreaks; GI.2/GI.6, 18 outbreaks; GI.3b/GI.3, 14 outbreaks; GI.4/GI.4, 21 outbreaks; GI.8/GI.8, one outbreak; GI.d/GI.3, four outbreaks; and GI.e/GI.13, one outbreak. The current study appears to be the first to have identified the recombinant form, GI.2/GI.6. Whereas GI.2/GI.6 and GI.3b/GI.3 outbreaks occurred with equal frequency in both healthcare and non-healthcare settings, GI.4/GI.4 occurred predominantly in healthcare settings. GI ORF 1/ORF 2 genotypes found in the eight outbreaks involving GI + GII norovirus were GI.2/GI.6, GI.3b/GI.3, and GI.4/GI.4, indicating GI genotypes in GI + GII outbreaks were similar to those found in outbreaks involving GI alone. Apparent differences in the evolution of different GI genotypes were noted. GI.2/GI.2, GI.2/GI.6, and GI.4/GI.4 strains tended to undergo periodic shifts in nucleotide sequence whereas various GI.3b/GI.3 strains tended to circulate simultaneously.

Evaluation of the RIDA(®)QUICK immunochromatographic norovirus detection assay using specimens from Australian gastroenteritis incidents.

A range of laboratory methods is now available for the detection of norovirus, a major cause of gastroenteritis. Recently, a commercial immunochromatographic assay for norovirus detection, the RIDA(®)QUICK assay, has become available, but there is still only limited information on its efficacy. This study examined the sensitivity and specificity of the RIDA(®)QUICK assay, using faecal material received for testing in a major diagnostic/reference laboratory in Australia. The sensitivity of the assay was found to be 83% and the specificity was 100%. No false positive norovirus results were found and the assay did not cross-react with common faecal viruses such as rotavirus, astrovirus, sapovirus and adenovirus. The assay was less reliable for genogroup I (GI) noroviruses than for genogroup II (GII) noroviruses. Genotypes detected by the assay included GII.1, GII.2, GII.3, GII.4, GII.6 and GII.7. The assay failed to detect any GI specimens in the test group. Genotypes not detected included GI.4 and GI.6. The assay was simple and quick to perform. It is valuable in a point-of-care situation or as a backup in a laboratory where a rapid initial norovirus result is required.

The effect of fecal turbidity on norovirus detection by reverse transcriptase polymerase chain reaction.

A 10-min fecal preparation results in greater specimen turbidity than a 45-min protocol, but reverse transcriptase polymerase chain reaction (RT-PCR) norovirus test sensitivity is essentially the same. Feces processed so that particle size does not exceed approximately 560 nm do not display greater norovirus RT-PCR inhibitory effects than those that have undergone greater purification.