A number of Zika virus cases are being reported in Southeast Asia over the past couple of weeks, of which many cases are believed to be of locally transmitted infection. Prevalence of local Zika virus strain in the region puts forth a question on the possibility of immunity against the disease.
Zika virus was first identified in Southeast Asia in the 1960s and in the next 50 years multiple sporadic cases were reported in many countries including Thailand, Malaysia, Singapore and Cambodia. After about half a century, a potentially serious outbreak involving 300 Zika virus cases is reported in Singapore just the past two weeks.
Eventually, the Ministry of Health's National Public Health Laboratory of Singapore sequenced the first reported three Zika virus strains, two cases from Sims Drive/Aljunied Crescent cluster and one infection acquired out of the country. Analysis showed that the sequence of Zika virus strain acquired from out of the Singapore was similar to the strain found in South America.
The report said that the result is in accordance with the fact — the patient's travel to Brazil two weeks before he developed the symptoms. The other two strains from patients who did not travel to any of the countries with an ongoing infection had sequences similar to that of Zika virus that has been circulating in the region for decades.
The researchers also noted that there is currently no evidence to explain the similarities and differences between the locally transmitted strain and South American strain in terms of type or severity of the disease.
Given that Zika virus has prevailed in Southeast Asia for a long time, it makes sense to believe that people from the region could be immune to the mosquito-borne Zika virus infection.
Jamal Sam, a virologist at the University of Malaya in Kuala Lumpur, said that there is ample evidence that the Zika virus has been in Southeast Asia for quite some time. And since there is a possibility that the virus could be infecting people silently for decades, people could be immune to the virus.
Sam added that a person infected by the virus once, won't probably get it for the second time. While it seems possible, it is not yet certain how immune people are to the virus.
However, the immunity theory may or may not work, said Jasper Chan, a microbiologist at the University of Hong Kong.
"Microcephaly, Guillan-Barre and all the other concerns about Zika are still a threat to people in this region" said Chan, until it is clearly established that people are immune to the infection. "The virus could spread explosively or not. We'll have to wait and see how the story unfolds."