What is Zika Virus?

November 04, 2019, 0 comments, on Mosquito Facts

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Zika is the name of a forest in Uganda where the virus was discovered in 1947(1) (2). This virus is from the same family as dengue and yellow fever. After raising in Africa in the 1970s and in 2007 in the Pacific, it has recently resurfaced in the Caribbean since 2013 to 214 and is growing strongly in South America since may 2015 particularly in Brazil (500 000 to 1 300 000 cases) (3).

It is not fatal and causes the same symptoms as fever in adults, but it seems to be associated with defects in babies of women affected during their pregnancy, although this remains to be verified.

Which mosquitoes which transmit Zika and how?

These are the female Aedes mosquitoes, recognizable by their black and white stripes on the legs, that carry the virus. This is especially the Aedes aegypti, native to Africa but also Aedes albopictus (mosquito Tiger, as vector of dengue and chikungunya) native to Asia also present in Africa and South America and recently expanding in Europe and North America (1).

Transmission occurs through the saliva of the mosquito, when a mosquito bites an infected person and goes after towards a healthy person. There is a possibility of contamination by blood transfusion (4).

What health effects known to date?

In adults

In fact in 70% to 80% of cases, no symptoms are observed, so patients are difficult to identify. Otherwise symptoms appear 3-12 days after the bite and are flu-like (fever, headache, body aches, evoking those of dengue or chikungunya). In some sensitive individuals, the virus can cause conjunctivitis or pain behind the eyes, as well as swelling of the hands or feet.

Pregnant women and fetus

This is where lies the most important concern. Zika virus could cause severe malformation called microcephaly (reduced cranial perimeter), responsible for irreversible mental retardation. In Brazil, the high increase of Zika could be associated with a strong increase in the number of babies born with microcephaly (more than 400 confirmed cases and 3 200 cases under study, versus 150 cases per year between 2010 and 2014) (5) and an increase in the number of cases of syndrome Guillain-Barré (may cause paralysis of the limbs and face) (6). The presence of Zika was identified in the amniotic fluid of 2 women whose fetus observation showed microcephaly. But the World Health Organization (WHO) recognizes that a direct relationship has not been proven to date. Some scientific research suggests that co-infection with another virus would be necessary.

Which areas are the most affected?

Zika virus is spreading at the moment especially in Central America and South America as it can be followed on the updated maps of the CRC website (Centers for Disease Control and Prevention):  www.cdc.gov 

Confirmed cases of the virus have been detected in several countries in South America and Central America: Brazil (since May 20015) and Colombia, Ecuador, Paraguay, Salvador, Venezuela, Suriname, Guatemala, Honduras, Puerto Rico, Haiti, Mexico (since october 2015 in these countries).

To date, the French departments of Guyana (15 cases), Martinique (47 cases), Guadeloupe (2 cases) and Saint Martin have been also recently hit.

Potentially the virus is also found in Africa and Asia where it had been observed in 1970, but the epidemic has not developed. In Africa: Uganda, Tanzania, Egypt, Central African Republic, Sierra Leone, Gabon and Senegal and in Asia and Pacific: India, Malaysia, Philippines, Thailand, Vietnam and Indonesia, New Caledonia, the Cook Islands and Easter Island.

The WHO recommends monitoring to keep under surveillance all countries where dengue is already present with Aedes mosquito : in Central America, most of South America, sub-Saharan Africa, India and Southeast Asia (over 1/3 of the world population).

What is the risk for Europe and North America?

So far, two cases were reported in Spain, 3 in the UK and 12 in the US (travellers who recently visited the areas already affected by the virus).

The expansion of Zika fever could occur in areas where Aedes mosquito is already present and where a person already infected with Zika spend time. In metropolitan France, the Tiger mosquito (Aedes albopictus) is present in over 20 southern departments.

The WHO has declared in bebruary 2016 it was a "global health emergency".

How to prevent and treat Zika fever?

Tests for detection of Zika and other virus are already available (developed in particular by the Pasteur Institute) and are being deployed in South America to help for fighting against the epidemic.

There is not yet known cure or vaccine against the disease (a vaccine has been approved in several countries for the dengue virus). Thus only the symptoms can be treated but aspirin should be avoided because it can lead to bleeding.

The best way to protect people from the disease Zika is to avoid bites by the use of effective and non-toxic repellents, especially for pregnant women, to wear protective clothing (long sleeves, pants) as well as use mosquito nets.

References

1. Higgs S. Zika Virus: Emergence and Emergency. Vector Borne Zoonotic Dis. 2016 Jan 29.

2. Dick GW, Kitchen SF, Haddow AJ. Zika virus. I. Isolations and serological specificity. Trans R Soc Trop Med Hyg 1952;46: 509–520.

3. Dyer O. Zika virus spreads across Americas as concerns mount over birth defects. BMJ2015;351:h6983.

4. Musso D, Nhan T, Robin E, Roche C, et al. Potential for Zika virus transmission through blood transfusion demonstrated during an outbreak in French Polynesia, November 2013 to February 2014. Euro Surveill 2014;19:pii/20771.

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