India’s Ministry of External Affairs confirmed, on September 1, 2016, that of the 115 cases of Zika virus (ZIKV) infection in Singapore, 13 Indian nationals had tested positive. This makes a point to worry – is the virus on its way to India?
A study based on analysis of climate, travel and mosquito breeding, conducted by UK based The Lancet, projected that the virus would affect 2.6 billion people in Asia and Africa while placing countries like India, China, Pakistan, Bangladesh, Nigeria, Vietnam and Philippines at greater risk.
Discovered in Uganda’s Zika forests in the year 1947, this virus was anonymous till it invaded Brazil and spread through the Americas within a span of one year. Brazil still being the epicentre of Zika virus disease, the virus has a presence in about 33 countries today.
Until the disease went to an epidemic scale in Brazil, in 2015, it was treated as a mild self-limiting illness because the affected people had no significant, or may be mild, symptoms. But now, with reports of the disease causing adverse health effects, it is considered a serious issue.
In February 2016, World Health Organisation (WHO) declared Zika fever a global emergency and a public health issue of international concern leading to birth defects and neurological problems such as Guillain-Barre syndrome – a rare disorder that can cause muscle weakness and paralysis in adults. Zika infection during pregnancy leads to birth of babies with small head circumference or microcephaly that causes brain disability. According to WHO report in August 2016, since 2015, 70 countries and territories reported evidence of Zika virus transmission.
What is Zika?
Zika belongs to genus flavivirus and family Flaviviridae. Zika is related to other flaviviruses such as dengue virus (DENV), yellow fever virus (YFV), Japanese encephalitis virus (JEV) and West Nile virus (WNV). Researchers from Purdue University, USA, first deciphered the structure of the Zika virus. The team also identified regions in the structure, where it differs from other flaviviruses. The findings were published in the Science magazine.
Aedes aegypti and Aedes albopictus (Asian tiger) mosquito transmits the Zika virus. Incidentally, the former also spreads dengue and chikungunya viruses. The virus can spread through sex and blood transfusion too.
The virus, responsible for disease outbreak in French Polynesia and other Pacific Islands in 2013 and 2014, is now causing infection in America and remains an Asian strain.In India, we already have dengue and chikungunya viruses ravaging us. The symptoms of both diseases are very similar to Zika infection causing fever, joint pain, rash, headache and red-eyes.
Available diagnosis of Zika infection involves detection of viral nucleic acid by RT-PCR and the detection of IgM antibodies using IgM-capture enzyme-linked immunosorbent assay (MAC-ELISA) in blood. Reliable procedures for testing of prenatal Zika virus infections are not available yet.
As in case of other viral infections, treatment for Zika infection includes only symptomatic treatment. Findings published by researchers from Singapore, in the Nature, reveal that ZIKV is thermally stable and is able to survive in semen, saliva and urine. Scientists speculate that antibodies or drugs that destabilize ZIKV can help limit the spread of the virus and curtail the infection.
No vaccine is developed yet to prevent Zika infection. The only prevention is controlling mosquito population and avoiding mosquito bites. Insect repellents containing DEET (N,N-diethyl-meta-toluamide), eucalyptus oil are effective against mosquitoes. Window net, bed mosquito net and permethrin treatment for clothing can keep mosquitoes at bay. It is important to cover the exposed skin to be safe from bites.
The US Centres for Disease Control and Prevention (CDC) has issued a travel alert appealing women of childbearing age to avoid countries where Zika is endemic and to women in countries with Zika to avoid getting pregnant.
Despite the fact that several Indians travel to Singapore for business or pleasure, India has not yet issued any travel advisory for its residents. It is safer to avoid unnecessary travel to areas endemic to Zika and unprotected sex with partners who may be at a risk of Zika virus infection.
Is Zika a threat for India?
In India, we already have A. aegypti mosquito. Our climate, especially rainy season, being conducive for mosquito breeding, it would be easy for Zika to thrive and spread infection. Since the signs and symptoms are quite similar to dengue or chikungunya, Zika infection could be easily mistaken.The relief lies in the immunity. After facing dengue or chikungunya, it is possible that Indians have developed immunity to mosquito-borne virus infections. Interestingly, in the Journal of Immunology, scientists have listed Zika infection as one of the 15 different insect-borne diseases in the year 1953. In this study, blood samples were obtained from indigenous residents of 38 localities in 6 states of India and tested for neutralizing antibody against each of the 15 viruses including Zika.
According to Dr. Kirti Sabnis, infectious diseases physician at Fortis Hospital, Mumbai, there are no confirmed cases yet in India. Initial infection with Zika may render life long immunity but no definite studies have been done until now.
According to the Indian Journal of Medical Research (IJMR) article: Zika virus: Indian perspectives, till now, “the only report on the possible presence of ZiV (Zika virus) in the Indian subcontinent is the detection of antibodies against ZiV (16.8 per cent prevalence) mostly in the Bharuch district of the then Bombay State, Gujarat and Nagpur in 1954, which could be a result of cross-reactivity with other flaviviruses as dengue was found prevalent in these areas.”
The future outlook
Indeed, it is difficult to diagnose Zika infection where dengue is endemic. Also, with nonspecific symptoms being mild, laboratory diagnosis is difficult. The spread of Zika continues as long as A. aegypti is the primary vector. The scary part is the risks of Guillian-Barre syndrome and microcephaly.
Experts blame globalization, urbanization and environmental factors for the emergence of Zika virus.
The growing population of India needs potable water and safe water storage facilities for household use as improper storage can make ideal breeding ground for A. aegypti to add to the threat of mosquito-borne viral diseases.
At present, Zika does not seem to be a threat for Indians but we have to look for newer mosquito control measures, adopt newer strategies to get rid of mosquito breeding places and adopt effective medications. Research thrust on vaccine development should be the priority to protect people against Zika virus infection.
Featured Image: A.aegypti is one transporter of Zika virus