SINGAPORE - Sequencing analysis of the Zika virus found in two of the patients from the Aljunied Crescent, Sims Drive cluster has indicated that the virus likely evolved from a strain that was already circulating in South-east Asia.

The virus from these two patients was not imported from South America.

The sequencing was completed by the National Public Health Laboratory and A*STAR's Bioinformatics Institute.

"The analysis found that the virus belongs to the Asian lineage and likely evolved from the strain that was already circulating in Southeast Asia," the Health Ministry said.

The research team will release more details shortly, it added.

There are 26 new cases of Zika infections in Singapore as of noon on Saturday (Sept 3). This raises the total number of locally-transmitted cases of the virus to 215.

Of the 26 cases, 24 are linked to the Aljunied Crescent, Sims Drive, Kallang Way and Paya Lebar Way cluster, the Ministry of Health (MOH) and the National Environment Agency (NEA) said in a joint statement.

Two patients have no known links to any existing cluster, but authorities did not say where they live.

NEA has been continuing with mosquito control operations in Aljunied and Bedok.

As of Friday, 83 breeding habitats – comprising 49 in homes and 34 in common areas or other premises – have been detected and destroyed.

Outreach efforts are continuing to raise awareness of the fight against Zika.

While outdoor fogging and spraying of insecticides continue in areas where Zika cases were found, it is not a sustainable way of controlling the mosquito population, NEA said.

"New batches of mosquitoes will continue to emerge until all breeding habitats are found and removed... source reduction is still a more effective and sustainable strategy," it said.