Zika virus – everything you need to know

Pregnant women are being advised to avoid affected countries

If you follow the news, you’ve probably read about the Zika virus and the panic over how fast the infection is spreading. Anything that causes people to panic can lead to paranoia in the media, which can sometimes obscure the facts of the matter. Although symptoms aren’t as bad as you might expect, the spread of the infection is alarming so it’s worth knowing the details.

The virus

Zika is a virus transmitted by mosquitoes. It was first found in 1947 when it was isolated from monkeys in Uganda. The following year it was discovered in mosquitoes and was eventually isolated from humans in 1954. There are two species of mosquito that are vectors for the virus: Aedes egypti and Aedes albopictus. These mosquitoes have a huge distribution and are found in over 100 countries worldwide. The virus, however, was relatively rare just a few years ago and only found in several countries in Africa.

The mosquitoes themselves tend to be found around buildings in urban areas and bite most often in the early morning and late afternoon. Using repellents and screens is the best preventative measure. Although almost all cases involve transmission from the mosquitoes, the virus has been found in semen and there at least 2 cases of sexual transmission of the virus. It’s extremely rare but something else to keep in mind.

The infection causes fever, rash, muscle pain, conjunctivitis, and headaches. As unpleasant as these are, the symptoms are mild and usually last only a few days. The good news: nobody has died from the infection. The bad news: there is no cure and no vaccine, so we have to accept that people will become infected and their symptoms will need to be treated.

The outbreak

Until recently, cases of human infection were rare and restricted to several African countries including Uganda and Nigeria. The first South Pacific outbreak began in 2007 when Zika was discovered on the Yap Island in the Federated States of Micronesia. In 2013, an outbreak occurred in French Polynesia and spread to Cook Islands, New Caledonia, and Easter Island. Another outbreak was discovered in Brazil last year and it has since spread to 23 countries in the Americas where millions of people will be infected over the next year. There have been 31 cases in the United States but they have all involved people travelling from affected countries. The US has had the Aedes mosquitoes since the 1980s but they don’t seem to be carrying the virus yet. It only took two years for the virus to go from relative obscurity worldwide to a devastating outbreak on several continents. Why so suddenly? I don’t have the answer but climate change and increased travel are going to be factors.

Birth defects

The virus doesn’t kill people and the symptoms are mild, so why the fuss? The outbreak in Brazil has accompanied a dramatic increase in births with microcephaly, a birth defect where the head is abnormally small. The brain doesn’t develop normally in these children and can result in learning difficulties, walking difficulties, seizures, and problems with sight and hearing. There is no direct evidence that the Zika virus is responsible but the timing alone is enough to raise suspicion. Cases of microcephaly in Brazil increased as the virus begun to spread. There were 167 cases in 2013, 147 cases in 2014, and an overwhelming 2,782 cases this year. The current tally for Brazil is 3,500 cases. Infection from Zika would make sense as the rapid viral outbreak could explain the absurd 1000+% increase in cases and we know that microcephaly can be caused by infections including toxoplasmosis, which I wrote about yesterday.

MRI scans showing brains of (i) someone with normal brain development and (ii) someone with microcephaly. Image © Yale University.

Global concern

There are many reasons to be concerned: the mosquito virus vectors are found worldwide so the virus could spread very far; it might be causing birth defects; people in newly affected regions have no immunity; there is no cure or vaccine; and the majority of injected people don’t actually show symptoms, which is probably contributing to the outbreak as people don’t realise they’re infected. The World Health Organisation (WHO) is deeply concerned and has created an emergency committee to address the outbreak. Pregnant women in several countries have been advised not to travel to affected countries because of the possible connection to Brazil’s microcephaly epidemic.

Do we need to worry here in the UK? The virus and mosquitoes are found in tropical regions, but their distribution is shifting due to climate change. It’s unlikely we will have an outbreak here, but we may see cases of infected travellers returning to the UK. The link between Zika and microcephaly hasn’t been confirmed but seems very likely, so pregnant women should definitely be wary of travelling in affected areas. My biggest concern is that both Zika and microcephaly seem to be worst in Brazil and that’s where so many people are heading this year for the Olympics in Rio. The Brazilian president has declared war on the mosquitoes but it’s unlikely the government can improve the matter before the event brings so many visitors from all over the world.

Click here to see World Health Organisation information on the virus.

Main image © Flickr/John Tann