The Ministry of Health (MOH) confirmed yesterday (3 Sep) that 26 new cases of locally transmitted Zika virus infection have been detected in Singapore, bringing the total number of locally-transmitted cases to 215. Of these, 24 cases are linked to the Aljunied Crescent/ Sims Drive/ Kallang Way/ Paya Lebar Way cluster. Two cases have no known links to any existing cluster.
The joint-statement by MOH and the National Environment Agency (NEA) further said that the National Public Health Laboratory has worked with A*STAR’s Bioinformatics Institute to complete the sequencing analysis of the Zika virus in two patients from the Aljunied Crescent/ Sims Drive cluster. The results show that the virus belongs to the Asian lineage and likely evolved from the strain circulating in Southeast Asia. The virus from these two patients was not imported from South America. The research team will release more details shortly.
Commenting on the sequencing analysis of the Zika virus in the two patients, Professor Paul Ananth Tambyah said information that the results showing that the strain is an Asian one and not South American, is very important information. Prof Tambyah is the President of the Society of Infectious Diseases (Singapore) and Secretary General of the Asia Pacific Society of Clinical Microbiology and Infection.
He said that it is likely that this strain has been circulating in the region for decades. “That may mean that older Singaporeans and most of the people in the region may be immune from previous exposure,” he added.
Pointing to a National Center for Biotechnology Information report, Prof Tambyah suggested that while the Asian strain is related to the South American strain via Polynesia, it is genetically distinct.
Flaminia Catteruccia, associate professor of immunology and infectious diseases at Harvard T.H. Chan School of Public Health, in January of this year said that the Zika virus in Brazil may be mutated strain.
She said: “If Zika is the causative agent behind the surge in microcephaly—and possibly also Guillain-Barré syndrome, an autoimmune disease of the nervous system now on the rise among adults in Brazil—this may demonstrate that the virus has adapted to the human environment and may have mutated to become more pathogenic to humans.”
The connection between Zika and microcephaly first came to light only last year in Brazil, which has since confirmed more than 1,800 cases of microcephaly. Commenting on the question of if the Asian strain would cause microcephaly, Prof Tambyah said: “That is the $64 million (or more) question. We will need to find out as it is likely that most of the historic infections in the past in the region have been in children not in women of childbearing age.”
The Zika virus has been in Asia and the Pacific for roughly six decades but its symptoms had caused little concern in the area. The Associated Press reported recently that the virus appeared in Asia in the 1960s, “in Indonesia, Malaysia, India, Cambodia, Vietnam, Thailand, the Philippines and Pakistan, but no widespread cases have been reported and symptoms have typically been mild and similar to dengue and chikungunya, which may have helped mask its presence.”