Zika virus is a single-stranded RNA virus belonging to the virus family Flaviviridae and genus Flavivirus. Zika Virus disease or simply Zika is a mosquito-borne disease caused by Zika Virus. In recent years Zika outbreaks were reported from Africa, Americas, Western Pacific and Southeast Asia. In 2016, World Health Organization (WHO) declared a public health emergency over the alarming spread of the Zika virus.
History:
Zika virus disease was first reported in Rhesus monkeys of Uganda in 1947. Human infection was first reported from Uganda and Tanzania in 1952. Later sporadic human cases were detected in Africa and South Asia. First Zika outbreak was reported from Pacific island of Yap in 2007. In 2013, there was Zika outbreak in French Polynesia, during which the neurological disorder Guillain-Barré syndrome was linked to Zika infection. In May 2015, there was a severe outbreak in the Americas (Brazil and Colombia) and Africa (Cabo Verde). During this outbreak, Brazil reported the association of Zika virus infection with Guillain-Barré syndrome and microcephaly.
So, human Zika virus infection have changed from an endemic disease causing mild illness in equatorial regions of Africa and Asia, to larger outbreaks causing serious neurological disorders and microcephaly in new areas. In coming year, it will continue to spread to newer areas, specially through international travel.
Transmission:
Zika Virus is primarily transmitted by Aedes mosquitoes, which also transmits yellow fever, dengue and chikungunya. The virus enter human body through the bite of infected Aedes mosquitoes, mainly females of Aedes aegypti. There is also possibility of sexual transmission. In a pregnant woman, Zika can spread to her unborn baby.
Symptoms and complications:
About one in five people develop visible symptoms. Common symptoms include fever, skin rashes, headache, joint pain, muscle pain and red eyes. Symptoms usually lasts 2-7 days. As the infection is usually mild, hospitalization and deaths are rare.
But in recent year, Zika virus disease is linked with auto-immune complications, which may lead to muscle weakness and paralysis (Guillain-Barré syndrome). In pregnant women, this disease may result in fetal malformations and Microcephaly (birth defect where infant’s head is smaller than normal head).
Dignosis and treatment:
Based on symptoms and recent visit to endemic areas, Zika virus infection may be suspected. Presence of Zika virus RNA in the body fluids (blood, urine or saliva) confirms the infection. So, laboratory analysis of body fluids is essential to diagnose Zika disease. The primary diagnostic test for Ziva virus infection is reverse transcriptase polymerase chain reaction (RT-PCR) testing. After that serological tests such as MAC ELISA and MIA are done to identify the antibodies.
There is no vaccine for Zika disease. The effect of the disease is mostly mild. Many patients recover without any specific treatment. Doctors recommend rest, rehydration by drinking plenty of fluids and use of common medicines for fever and pain.
Prevention:
Avoiding mosquito bites is the best way to avoid Zika virus disease. Mosquito avoidance measures may include use of repellents, use mosquito nets during night, wearing long-sleeved shirts and long pants to minimise exposed skin, avoiding visit to endemic areas etc. Contact between mosquitoes and people can be reduced by destroying mosquito breeding sites, using physical barriers and spraying of insecticides.
Zika virus Vaccine:
Scientists around the world are working hard to develop Zika virus vaccines. In February, 2016, Hyderabad-based Bharat Biotech announced the development of world’s first Zika vaccine – Zikavac. They have two variants – one inactivated and one recombinant. The vaccines are still in pre-clinical trial stage.