Zika Virus: who, what, when, where, how?

Health, Science 2016-02-16

Over the past weeks and months you will have undoubtedly seen headlines or heard news reports about Zika virus. The World Health Organization (WHO) has now declared the Zika virus an international public health emergency due to the threat it poses to pregnant women and babies. In this short blog I will aim to cover the basics of the virus: what it is, how it’s spread, who it affects, where it’s affecting and also why it’s suddenly become a global emergency despite being identified over 60 years ago.


Surprisingly to some, Zika is not a new virus and it was in fact first recorded in 1947 in rhesus monkeys in Uganda. It was later identified in humans in 1952, again in Uganda and the United Republic of Tanzania. Since then it has been reported in the Americas, Asia, other parts of Africa and the Pacific.  See map below to understand how the virus has travelled.


Zika virus is transmitted by mosquitos, specifically Aedes aegypti, which carry the virus and bite humans causing them to become infected. This type of mosquito is particularly effective at carrying this virus and it’s also the primary vector of the yellow fever, dengue, and chikungunya viruses. This genus of mosquitos is also better adapted to live amongst humans compared to others as they are able to thrive in smaller bodies of water, even as small as a bottle cap, making them very difficult to avoid.


The best way to prevent the spread of the virus is by minimising exposure to mosquitos by removing their source or avoiding contact.  This can be done using insect repellent, covering up small bodies of water, keeping doors and windows closed and sleeping with mosquito nets.


What’s interesting about Zika is that in many instances it remains undiagnosed as symptoms are very subtle and in 80% of cases there are no symptoms at all. If a patient does display symptoms, they usually manifest as minor fever, headache and a body rash. The most worrying thing about Zika, though, is the links that have been drawn in more recent years. Researchers noted that many people infected during the Brazil and French Polynesia outbreaks later developed Guillain-Barré syndrome, a rare and serious condition of the peripheral nervous system. Zika virus has also been linked with microcephaly, a rare neurological condition in which an infant’s head and brain are significantly smaller than they should be. Since the outbreak in Brazil in 2015 there has been a 20-fold increase in the number of cases of microcephaly. For this reason, pregnant women are being discouraged from travelling to regions affected by the virus, and those planning to get pregnant should delay it if possible. It’s worth noting, though, that if you’ve had the virus it is perfectly safe to have a child in the future as the virus leaves the blood system after a few weeks.


As the symptoms of Zika itself are relatively minor, there are no specific treatments for it other than rest and staying well hydrated.


The reason Zika virus has begun to spread so fast across South America at the moment is due to a lack of background immunity within the populations there. Added to this is the fact that Aedes aegypti mosquitoes are densely populated in this region and the environment is perfect for them to thrive. This combination has resulted in a rapid spread of the virus within the last year in South America.


With 16,000 athletes and 600,000 spectators due to arrive in Rio this August for the 2016 Olympic games, this outbreak has come at a very critical time for Brazil. Some countries and athletes are beginning to discuss whether they will be attending due to the risk of Zika virus. Some are calling for the Games to be cancelled or postponed, but the spokesman of the Rio Olympics said that cancellation “has never been mentioned”. Experts of infectious disease believe that Brazil is making a huge effort to tackle the virus and that factors such as it being held in one city and within colder months should be able to reduce the risk of Zika to an acceptable level. At the moment no countries or athletes have officially pulled out, although many will continue to assess the risk up until August.


Scientists have still not been able to prove a definitive link between Zika and microcephaly so this remains the biggest focus of their research. The WHO recommends all people to avoid travel to affected regions and delay pregnancies where possible. If you’d like to find out more information about this virus head to the WHO website: http://www.who.int/mediacentre/factsheets/zika/en/.


Have you got any questions about Zika? Tweet them to me at @EmilyAtNotch!