Zika and dengue mosquito

This Aedes aegypti female was from a strain of mosquitoes named LVP-IB12, an acronym representing the fact that these mosquitoes were derived from the Liverpool strain (LVP), and that they were inbred 12 times (IB12), in order to create a more homogeneous genotype. Also, of great importance is the additional fact that this specie is being used in the A. aegypti genome sequencing project. Though the mosquito’s geographical origin is not known, it is believed to be somewhere in Africa. (James Gathany/CDC)

The mosquito-borne Zika virus is likely to spread to all countries in the Americas except for Canada and Chile, according to the World Health Organisation. The tropical disease has been linked to birth defects...and the rapid spread of the virus is raising concerns among health authorities. Late last week the U.S. Centers for Disease Control (CDC) issued an updated travel alert warning pregnant women to delay travel to 22 destinations..mostly in Latin America and the Caribbean that have seen outbreaks of the virus.

In the middle of 2015, the Zika virus started to show up in significant numbers in Brazil and in other parts of South America.  Then, authorities in Brazil saw a huge spike in the number of babies born with microcephaly, a condition in which the child is born with an abnormally small head and missing or underdeveloped parts of the brain.  Microcephaly usually occurs sporadically; for instance, in the UK, they see one case per 10,000 births per year.  By comparison, in Pernambuco in northeast Brazil, they've seen 300 cases per 10,000 births or 300 times the usual incidence. As of the weekend, Brazil authorities say around 4,000 babies have been born with microcephaly just since October of last year.

Until it arrived in Brazil, Zika wasn't considered that dangerous.  It's possible that in Brazil, the disease found the perfect breeding ground: lots of mosquitoes to transmit the virus and lots of Brazilians to get infected because they had no prior immunity.  Like Dengue fever, any virus transmitted by a mosquito can spread rapidly.  As for the possible link between Zika and birth defects, the US Centers for Disease Control recently found the fingerprint of the virus in the placentas of women who gave birth to affected babies.  At least nineteen of the babies born with microcephaly have died.  Some believe the Zika virus could be to unborn children today what rubella or German measles was a couple of generations ago. 

The World Health Organization is investigating a possible link between Zika virus and Guillain-Barre syndrome in El Salvador.  Guillain-Barre is a rare disorder in which your body's immune system attacks your nerves causing severe muscle weakness and tingling  usually beginning in the legs and spreading upward to paralyze most of the body. Most people with the condition must be hospitalized to receive treatment. Guillain-Barre has also been reported in patients with likely Zika infection in French Polynesia and Brazil.

The incubation period for the Zika virus is anywhere from three to 12 days.  Of every ten people infected, 8 have no symptoms; the other two get mild fever, joint and muscle aches and pains, red eyes, a rash, weakness or lack of energy, malaise and headaches.  Those who get symptoms usually feel better after two to seven days, and seldom need to be admitted to hospital. Most recover fully without complications.  

The only treatments we have for Zika virus are supportive - meaning acetaminophen or ibuprofen for fever, aches and pains.  There's no medication that kills the virus.  Brazil says it wants to develop a vaccine.  Experts say we don't have one yet simply because until now, there's been no market for it.  The Public Health Agency of Canada says women who are pregnant or who may become pregnant should consider postponing travel to a growing number of Zika hot spots including Brazil, Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde, and Samoa.  

Anyone who doesn't heed this warning and who visits a hot spot should take steps to prevent mosquito bites like wearing insect repellent as well as protective clothing and nets. If you're pregnant and have come back from a hot spot, you should be tested for the virus.  The Public Health Agency's National Microbiology Laboratory says it's able to detect the virus, and is in a position to test specimens at the provinces' request.

The World Health Organisation has said the virus won't likely make it it Canada. Does that mean Canadians can rest easy? In a statement, the Pan American Health Organization (PAHO), the regional office of the WHO, said that "Zika virus will continue to spread and will likely reach all countries and territories of the region where Aedes aegypti mosquitoes are found"  which means all countries in the Americas except Canada and Chile.

Parts of the U.S. could see homegrown outbreaks later this year. Puerto Rico and the U.S. Virgin Islands are at the most immediate risk.  The U.S. Gulf Coast has mosquitos that can carry the Zika virus.  Canada will almost certainly see imported cases.  Several U.S. states including Illinois, Hawaii, Florida and New York State have had imported cases.  Last week, authorities in Hawaii reported the first child born in the U.S. with microcephaly.  The baby's mother was pregnant while living in Brazil.  That's where authorities believe she got infected with the Zika virus.

The most recent reports have raised the question of whether Zika is a sexually transmitted disease.  There is one isolated case report from late 2015 in Brazil, and a published case report by the CDC from 2013. It makes sense that when you have the infection the virus would show up in bodily fluids.  But that does not mean the Zika virus is sexually transmitted - and does not account for the role of mosquitoes as vectors of the virus - which are responsible for the rapid spread of the disease in the Americas. 

I don't find this development particularly alarming.  No doubt we'll be receiving many more tidbits of information like this before the picture becomes clearer.  Still, we need to stay tuned for further details.  The story is far from over.