Malaysia: Norovirus discovered in lettuce

Despite improved sanitation, water supplies, and food safety, diarrhoea remains a common cause of illness worldwide. It is reported to account for approximately 1.8 million annual deaths in children <5 years of age (Bryce et al., 2005), making it quite necessary to explore etiological agents for diarrheal diseases.

Norovirus (NoV) is an important cause of acute gastroenteritis in children and adults and is transmitted by fecal-oral route.

Universiti Teknologi MARA researchers tested the lettuces for the presence of NoV, which were then examined by immunochromatography and reverse-transcription polymerase chain reaction techniques.

Stool samples were obtained from eight different hospitals in Peninsular Malaysia. Out of 168 stool samples examined, 45.8% were from children less than 5 years old and 22% were antigen positive. Due to small amount of fecal material left from this age bracket, NoV was not screened since it is already known that 90% in this age group are often infected with rotavirus (RV), which is the most common cause of severe diarrhoea in children.

From the remaining total screened, only 89% were screened for NoV and 9.3% were NoV genogroup II. By phylogenetic analysis, GII/3 and GII/4 were found to be the prevalent strains. Majority of these samples were closely related to GII/4 Nagano 2007/JP strains from Japan and one was closely related to GII/4 from Bristol, UK.

This study highlighted that the prevalence of NoV GII.4 strains (71.4%) were in concordance to other reports worldwide, with RV (22%) in the children <5 years old and NoV in 9.3% of the cases. In the lettuces tested , NoV antigen was not detected but by amplification of NoV gene, two (10%) were identified as GII.6 strain.

This study also provides valuable information on NoV genotype , which could be used for surveillance and vaccine strategy. The presence of both GII.4 and GII.3 are in concordance to other strains reported elsewhere in the world. This novel GII.4 variant, termed Hunter virus (Bull et al., 2006) have been identified as the etiological agent in 18 outbreaks investigated including The Netherlands, Japan and Taiwan in 2004 and 2005.

This study is the first report of NoV in lettuces in Malaysia. This preliminary study should be continued since NoV is now being identified as one of the common cause of diarrhea and is still under reported in Malaysia.

Provided by Universiti Teknologi MARA (UiTM)