Translated from the original Japanese by:- Kaede I <kaedesyrup@yahoo.com>

Monday 13 July 1998.

MOLECULAR EPIDEMIOLOGY OF ENTEROVIRUS 71 ISOLATED IN MALAYSIA AND JAPAN

The enterovirus 71 (EV71) is one of the major agents of hand-foot-and-mouth disease (HFMD) along with eneteroviruses Group A coxsackievirus 16 (CA16) and Group Acoxsackievirus 10 (CA10). EV71 is a common virus that has been isolated from all regions in Japan on an annual basis. More than 40 fatal incidences of EV71 infections were reported both in Bulgaria (1975) and Hungary (1978). Occasionally EV71 is known to cause severe neural complications. In Australia and the US, incidences of complications of disorders involving the central nervous system have been linked with EV71.

In Sarawak, Malaysia, an enterovirus infection among children involving fatal cases was reported in 1997. (See other page).  The Japanese National Institute of Infectious Diseases and the Malaysian National Institute of Medical Research jointly collaborated to isolate the enterovirus from fatal cases and HFMD patients in Sarawak and Peninsular Malaysia. Up todate, 15 strains have been isolated. According to molecular epidemiologicalanalysis, the isolated Malaysian EV71 (Sarawak type) strains from fatal and HFMD cases were identified to be all from the same genotype. The Malaysian Sarawak type EV71 compared with the known nucleotide sequences of the previous isolates (prototype strain BrCr and the 7423/MS strain (US 1987)) showed 80-86% RNA and 95% amino acid match indicating that the EV71 belongs to a different genotype group.

To compare the pathogenicity and viral characteristics of EV71 causing HFMD in Japan and the EV71 isolated in Malaysia, a molecular epidemiological comparative analysis of each enterovirus was performed. The strain that caused a small scale HFMD epidemic with fatal cases in Osaka showing encephalitis presumably due to EV71 infection was also analyzed. When the 40 EV71 strains isolated in the past and the strain found in Osaka were analyzed, it was found that they could be grouped largely into two. About 10 strains showed genotypic similarities with the EV71 isolated in Malaysia. The strain causing the fatal cases in Osaka was found to belong to the same genotype group as above. The rest of the Japanese EV71 strains showed considerable difference with the EV71 Sakura type.

Varying pathogenicity and symptoms depending on regions and seasons have lead researches to believe that different EV71 strains have different pathogenicities. Along with further research on EV71 isolated in Japan and other regions of the world, careful monitoring of the Japanese EV71 and their genotypes seems to be very important.

National Institute of Infectious Diseases,
Viral Division 2:
Hiroshi Shimizu, Andi Utama, Hiroshi Yoshida, Teruo Hagiwara, Tatsuo Miyamura

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