In a recent study, published in the journal Emerging Microbes & Infections, a multi-national team of researchers have traced the trail of the Zika virus from the forests of Africa to India and other Asian countries. Considering the concerning recent media reports on the mass detection of Zika virus infection in Jaipur, India, this study may throw light on the evolution of the disease and help develop control strategies against the fatal virus.
The Zika virus was first detected in a rhesus monkey in the Zika forest of Uganda in 1947. One year later, the virus was discovered in a mosquito species Aedes africanus, indicating its circulation among mosquito and monkeys. The infection then gradually spread to other parts of Africa and reached Asia. As per the World Health Organization’s classification scheme on the prevalence of this virus, India is in category 2, indicating ongoing transmission of this virus.
The researchers of the current study analysed the genomic sequence of the causative virus to understand its evolutionary history and dispersal pattern. “Many new sequences are now available from Zika virus infected humans in Asia, including Bangladesh, India, Indonesia, the Philippines, Singapore, Thailand, and Vietnam. These sequences may impact our interpretation of the early evolutionary history of Zika virus in Asia. We, therefore, re-visited the evolutionary events of Zika virus from its first emergence in Asia”, say the authors, talking about the motivation behind the study.
The findings of the study reveal that the virus entered India later than some of the other countries in Asia. “The Zika virus was first introduced to Southeast Asia during the 1950s, which then dispersed both eastwards and westwards. It was potentially first introduced from Africa to the Malaysian–Indonesian region and subsequently to India”, explain the authors.
But, why is it that we do not see the virus turn into an epidemic for so long? “The very low frequency of clinically apparent Zika virus infections and the difficulty in clinically discriminating the Zika virus infection from the infections caused by Dengue, and chikungunya virus were major factors in the failure to recognize the presence of Zika infections,” opine the authors. They also suggest that the Asian population might have developed a herd (community) immunity to the virus.
The findings of the study can help policymakers and healthcare professionals to understand the disease in its entirety and devise appropriate control measures. “Our findings reveal new features of the evolution and dispersal of this intriguing virus and may benefit future disease control strategies,” the authors say.