Friday, 5th Feb, 2016
Zika virus infection has been declared as a global health emergency on 1st Feb, 2016. The director General of World Health Organisation (W.H.O.), Dr Margaret Chan, made this announcement after W.H.O. emergency committee led by Prof David L Heymann of London School of Hygiene and Tropical Medicine made this decision.
Broad geographical presence of Aedes mosquitos (it is present in all continents except Antarctica), absence of immunity among people, lack of vaccine, and lack of rapid and reliable diagnostic test point to the possibility that Zika virus may spread globally and exponentially.
There are more than 1 million Zika virus infections all over the world by now. It is expected that there will be 4 million cases by the end of 2016. Cases have been reported from 24 countries from the Caribbean, Central America, South America, the USA, Europe and Australia, but the concentration is in the South America and Central America.
Zika virus was first detected in a monkey in Zika forest of Uganda in 1947. The virus was found to have infected a human in Nigeria in 1954. Subsequently, sporadic cases have been reported elsewhere in 2007 in South East Asia and Pacific Islands.
In 2013-14, there was an outbreak in French Polynesia. Many cases of Microcephaly and Guillain-Barre Syndrome were reported.
In May 2015, an outbreak of Zika virus infection was detected in Brazil. Later that year, there were many cases of Microcephaly reported from Brazil. Even though the exact relation between Zika virus and Microcephaly has not been confirmed, there is a strong suspicion of this causal relation. In 2014, Brazil had 147 cases of Microcephaly, but in 2015, it reported 4074 cases. Numbers have been rising exponentially. There is some confusion and uncertainty about the accuracy of Brazil’s reporting of Microcephaly cases however.
Since Zika virus infection has not been a focus for scientists and scientific research until quite recently, many things about it are unknown at this stage.
Zika virus is from Flavivirus family of viruses, just like Dengue, Chikungunya and Yellow Fever viruses. They are spread by Aedes (mostly Aegypti subtype but also Albopictus subtype nicknamed Asian Tiger mosquito in small numbers, particularly in South East Asia) mosquitos. Aedes mosquitos are found in abundance in many countries in tropical and subtropical region. They are also found in South Eastern USA and Hawaii. Albopictus subtype is found in 32 states of the USA. Aedes mosquitos are present in Northern Australia, and even in the international airport in Sydney, Australia.
Zika virus is transmitted by mosquito bites. Mosquitos get infected by biting infected persons. A few cases of sexual transmission have been reported. First case was reported in 2008 and the latest case was reported from Dallas county of Texas on 3rd Feb, 2016. Zika virus can be transmitted by blood transfusion. Recent reports suggest Zika virus is present in saliva and urine, although its significance is unclear at present
Only 20% of infected people have symptoms within 3-12 days after the bite. Symptoms include fever, joint pains, rash, headache and conjunctivitis (red eyes). Symptoms resolve within 2-7 days. 80% of infected people have no symptoms.
It is not a fatal infection generally and no long-term harm appears to occur to people except for rare occurrence of Guillain-Barre syndrome, a disease of nervous system, which can cause health problems for weeks, months or even years.
The most serious condition it is suspected to cause is Microcephaly, which means small brain and poor development of brain, with consequent long-term health and care issues for the child.
There is no readily available diagnostic test for Zika virus yet, and only few highly specialized laboratories can detect the virus by a Polymerase Chain Reaction (PCR)-based test.
There is no specific treatment yet. Supportive care-pain killers, Paracetamol, nourishment, fluids and rest- is what can be offered and needed.
There is no vaccine available yet. National Health Insitutes (NIH) of the USA is encouraging researchers to take up the research on Zika virus, and is willing to fund such research.
The best approach to deal with infection is to prevent the virus infection by avoiding mosquito bite and mosquito mitigation programme;
Mosquito bite prevention:
- stay in screened or air-conditioned rooms and avoid places where mosquitos stay and breed
- wear insect repellents
- wear long pants, full sleeve shirts, shoes and hats
- sleep under mosquito nets, which, unlike the case of Malaria infection, may not be as effective because Aedes mosquitos generally bite in the day, although they do bite in the night too
- proper cleaning of the surroundings
- proper waste disposal
- removing stagnant water collection and anything which can store even small amount of water in/around dwellings
- insecticide spraying/fumigation
- genetic modified mosquitos
Genetically-modified mosquitos (A):
- Oxitec-a genetically-modified Insect company is the world leader
- mosquitos are genetically modified
- they do not bite
- their offspring don’t survive
- they can replace the offending variety of mosquitos by more than 80%
- have been used in northern part of Brazil
- work in progress and more information to come
- a Melbourne-based Australia-led collaboration dedicated to wipe out Dengue worldwide
- project director of “Eradicate Dengue”-Prof Scott O’Neill
- by releasing Wolbachia bacteria-infected Aedes mosquitos, which are resistant to not only Dengue virus but also Zika virus
- Wolbachia blocks Zika virus infection of the mosquitos almost in an identical way to Dengue virus infection
- has been used in North Queensland
- this group is in discussion with some South American countries
- work in progress and more information to come
Until exact treatment and vaccines become available, the best approach obviously is prevention from mosquito bites.
- Centers for Disease Control & Prevention (CDC) recommends that women who are pregnant or want to become pregnant should not travel to countries where Zika virus infection is common. Highest risk of Microcephaly is likely to be in the first 3 months of pregnancy.
- Partners of those who have been to such countries should practise abstinence or use protection (Condom) consistently and correctly to avoid transmission by sexual intercourse.
- People who have travelled to such countries should not donate blood for 30 days, as per the recommendations from American Red Cross and NHS of the United Kingdom.
- if travel to South America is essential and can’t be avoided, people should use mechanisms to prevent mosquito bites.
Zika virus and India:
- unclear and uncertain scenario
- like Dengue virus, Zika virus may create significant problems in India
- Aedes mosquitos are present in abundance and can spread the virus after getting infected from biting a person with Zika virus infection
- there are sufficient chances for infected people (travellers) to bring Zika virus, which can infect Aedes mosquitos
- poor sanitation and poor waste disposal
- collection of water almost everywhere and Aedes mosquitos can breed even in a collection of very small amount of water
- dense urban population
- identical, if not worse, situation in the rural side
- inadequate availability of health facilities for a significant proportion of people, which may lead to delayed or no diagnosis, as well as treatment, of Microcephaly and Guillain-Barre Syndrome
- uncertain knowledge of the role of immunity against Dengue and other similar viruses, and its impact on Zika virus infection in the population
- vast population, leading to vast number of potential cases