First isolated from a rhesus monkey in the Ziika forest of Uganda in 1947, the Zika virus is a single-stranded RNA virus from the Flaviviridae family. It is related to the yellow fever, West Nile, dengue and Japanese encephalitis viruses. As with dengue and chikungunya, carrier female Aedes mosquitoes infect humans through their bites, which can then be transmitted between humans through mosquito bites. Zika virus can also be transmitted through sexual intercourse, maternal-foetus transmission and transfusion of infected blood.

Zika virus outbreaks have been reported in several parts of the world – Africa, Western Pacific and Americas. Majority (80%) of the affected individuals do not show any symptoms, and a few of them develop mild symptoms of fever, skin rash, body pain, joint pain and conjunctivitis. However, it was the major outbreak in Brazil in 2015 affecting almost 1.3 million people, subsequently spreading to 33 different countries that drew global attention. The virus had undergone some changes,affecting foetuses and adults. The infection was now also associated with congenital brain abnormalities, like microcephaly (smaller than normal head, which in turn causes several neurological complications like intellectual disability) and could trigger the potentially life-threatening Guillain-Barré syndrome (GBS), wherein the immune system attacks the peripheral nervous system, causing rapid onset of muscle weakness and paralysis  in children and adults.

Currently, there are no vaccines or antiviral drugs to combat Zika. The treatment is essentially symptomatic – rest, remaining hydrated and paracetamol to control fever and pain. However, a few vaccines under development are now entering Phase 1 of clinical trials, including one developed in India by Bharat Biotech.

While it is important to know the number of people infected with Zika virus, it is perhaps more essential to ascertain the percentage of Aedes mosquitoes carrying the virus, as they are the primary transmission agents. This would provide us with a better understanding of the spread of disease in the population.

The National Vector Borne Disease Control Programme (NVBDCP), which has been set up to control and prevent vector borne diseases like malaria, Dengue, Chikungunya and Zika should be more forthcoming and make its vector surveillance data public. NVBDCP should provide information like – how much fogging is being done? What is being used for fogging? Are they seeing any chemical-resistant mosquitoes in the fogged area? Are samples collected before and after fogging? Is there any overlap between dengue and Zika affected areas? Easy to understand maps with GPS/IRNSS coordinates would be a good tool to use by them to communicate these data. Most of the times when we talk about Zika (or other infections), we focus on what needs to be done from the patient side, and about public education and guidelines. In addition, it is also important to understand the efficacy of our vector control program.

Given that the Aedes bites during the day, mosquito nets are of little use to combat them. Fogging effects are short-lived and can indeed lead to a rise in fogging-chemical resistant mosquito population.

There are newer methods of vector control and surveillance that need to be actively explored by the NVBDCP and effectively communicated to the public. For example, India recently joined Australia led ELIMINATE Dengue Project. Wolbachia is a bacteria which infects a lot of insects. ELIMINATE project aims to use Wolbachia bacteria to infect Aedes mosquitoes in dengue areas and render them incapable of disseminating dengue and chikungunya viruses. A recent scientific paper in the journal Cell has reported that the same is true for Zika virus as well.

Another innovative approach is based on pyriproxyfen, a human-safe synthetic analogue of mosquito juvenile hormone, that female mosquitoes can themselves deliver to the larva, thus overcoming the limitations of search for breeding containers that are often unreachable to eliminate larval population. Release of sterile male mosquitoes to decrease the overall mosquito population is another approach. Yet another strategy is release of genetically-modified mosquitoes maintained on specific drugs (e.g. tetracycline) in the laboratory. When released, the mosquitos breed but offspring can not survive since the specific drug is absent from the environment. All the above approaches are being tested in various countries around the world and can produce dramatic (nearly 95%) reduction in the mosquito population.

While it is important for people to follow precautions to protect themselves and their loved ones from mosquito bites (mosquito nets, mosquito repellents and creams), it is equally important for them to maintain cleanliness at home and in their surroundings. However, with rapid urbanisation and constantly shifting personal and governmental priorities, vector control programmes need to be strengthened to allow innovative out-of-the-box approaches. Active governmental participation through policy decisions and proactive promotion can substantially affect our responses to various vector borne diseases plaguing India, including Zika.