Sequencing of Zika Virus Strains From Sims Drive/ Aljunied Crescent Cluster

The Ministry of Health’s National Public Health Laboratory (NPHL) and A*STAR’s Bioinformatics Institute (BII) have completed the sequencing of the virus strains of three live Zika cases found in Singapore. These cases comprise the first imported Zika infection detected in May 2016, and two local transmission cases from the Sims Drive/Aljunied Crescent cluster.

Key Findings

2.    The sequence of the first imported Zika case that was reported in May 2016, is similar to the strains currently found in South America. This finding is consistent with the patient’s travel history. He had travelled to Brazil just before he fell ill.

3.    The Zika virus strains found in the two locally-transmitted cases from the Sims Drive-Aljunied Crescent cluster were not recently imported from South America.These virus strains have sequences similar to strains of Zika virus which have been circulating in South-east Asia since the 1960s before the viruses spread to French Polynesia in 2013 and subsequently to Brazil in 2015.

Implications of Sequencing Findings

4.    The analysis of the virus found in two locally transmitted cases shows it belongs to the Asian lineage and likely evolved from a strain that was already circulating in South-east Asia. Currently there is no evidence from existing studies and from this sequence to indicate whether the differences between these strains and the South American virus correlate with differences in severity or type of disease. The virus sequence, when shared with the international community and compared with existing virus sequences, will help in tracking the global spread and evolution of the Zika virus.

5.    Correlation of virus strains with specific clinical manifestations will take long-term careful epidemiological studies as well as experimental studies in research laboratories.  Knowing the range and distribution of virus strains would also be useful in future testing of vaccines and various treatment strategies.

6.    MOH’s NPHL and A*STAR’s BII will continue to monitor and study the evolution of the virus in Singapore and the region. The sequences from their analyses will be made available on public databases for the benefit of the global scientific community, including the World Health Organization.