Mosquito-borne virus spreading around the world

While relatively benign to most, Zika virus can cause birth defects if pregnant women infected

The mosquito-borne Zika virus has reappeared after nearly a decade of obscurity. In December, the Public Health Agency of Canada (PHAC) confirmed the first case of Zika in the country from a traveller who had recently returned from El Salvador. The virus has also sprung up in the U.S. and U.K. in travellers coming from Central and South America.

Since the 1950s, the Zika virus has been circulating in small numbers in Africa and some regions of Asia. The virus spread to several southwestern Pacific island nations in 2007 and emerged in South America in 2015. The virus has spread to as many as 14 countries in Latin and South America. The virus does not spread directly from person to person. It is transmitted when a mosquito that has bitten an infected person bites someone else. Mosquitos that transmit the virus are not present in Canada, however their range may spread as the climate warms.

There have not been any recorded deaths resulting from Zika virus but it may have a connection to microcephaly, a condition in which newborns develop small heads and malformed brains after their mothers contract the virus while pregnant. Brazil has seen the largest-known outbreak of Zika since the virus entered the country in October, and the number of microcephaly cases there has increased by tenfold to nearly 4,000. In a report from Brazil’s health ministry, 49 of these babies with suspected microcephaly have died, and five were found to be infected with the Zika virus. Researchers at the University of Texas and in Brazil are working closely to examine the possible link between Zika and microcephaly in babies.

This month, the first case of Zika virus in a newborn baby in North America was confirmed. The baby was born in Hawaii with brain damage and was also infected by the Zika virus. The mother was living in Brazil in May 2015, where she contracted the disease.

Some individuals carrying the Zika virus display symptoms such as mild fever, rash, joint pain and eye redness. Most others show no symptoms. There is currently no treatment for the illness, and it disappears within a week when the person is well rested and hydrated. The current diagnosis for the disease is to check for antibodies that bind the Zika virus using a blood test. False positives are often seen in these tests, as Zika is closely related to the viruses causing yellow and dengue fever. All three of these viruses are carried by Aedes aegypti, an invasive mosquito species from Africa. In undeveloped areas with limited access to medical facilities, it is almost impossible to get an accurate test result, as most people living there are given vaccines against both yellow and dengue fever.

The PHAC advises travellers, especially pregnant women, to take precautions like using insect repellent, wearing long sleeves and long pants, and staying in well-air-conditioned places when visiting countries that are experiencing Zika outbreaks.

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