This summer, the Brazilian city of Rio de Janeiro will host the Olympics. Millions of athletes, officials, and tourists will arrive for two weeks of sports and cultural celebrations. Unfortunately, the last time Brazil hosted an international event on this scale, last May’s soccer World Cup, an unwanted visitor arrived from Asia or Africa: the Zika virus.
Named for the forest in Uganda where it was first isolated in 1947, the virus is spread by Aedes aegypti mosquitoes and related to Yellow Fever and Dengue, with similar but milder symptoms: muscle aches, a slight rash, and sometimes conjunctivitis or pink eye. If people who get it even realise they are sick, they probably just think they have a bit of a cold or flu. Symptoms last from a couple of days to a week at the most.
Aedes aegypti mosquitoes’s favourite food is people blood, and they make sure they get enough of it by living in or near human communities, biting during the day, and flying at a lower altitude so they increase their chances of finding bitable skin. They cannot, however, survive the cold temperatures that species found in Canada can survive, so we are unlikely to see the same epidemic conditions unless the virus is found to spread through sexual contact. This is possible because Zika is a flavivirus, related to Hepatitis C, but so far there has been only one suggested but unconfirmed case of sexual transmission.
Like many viruses, once you’ve had it, you won’t get it again, and in countries where it’s found, many people are immune, and of those who get sick, only people with an already weakened immune system are at risk of serious illness. But, in Brazil, over the last year, it’s been different. And this is where it gets frightening….
Because the virus is new to the Americas, populations don’t have the kind of “herd immunity” found in places where the virus is endemic. This means that more people will get sick from it because nobody has had it before. The local mosquitoes are the sort that can spread it: a mosquito bites an infected person, flies off and bites someone else, and passes the virus along. Unlike HIV, for example, which lives in blood but cannot be transmitted by mosquito bites, the mosquito’s saliva doesn’t destroy the virus.
No matter what species they are, all mosquitos breed in standing or stagnant water: ponds, bird baths, puddles, potholes, anywhere water collects. Because they like to live inside, however, Aedes aegypti mosquitos breed in flower vases and other domestic sources of water as well. They can breed in an amount of water as small as that contained in a bottle cap. The Brazilian army has announced plans to go door to door to try to eradicate any household standing water in some towns. El Nino has brought even more rain to the tropics this year, making it riskier for all mosquito borne illnesses such as malaria, West Nile, and more.
Unfortunately, the epidemic in Brazil has had an additional, very distressing element. Since the virus appeared in 2015, the number of babies born with microcephaly has increased 20-fold. The country usually sees about 150 cases a year: since October 2015, nearly 4,000 cases have been reported. In babies born with microcephaly, their heads are abnormally small and their brains have not fully developed. Microcephaly is rare and it can also be caused by other factors such as mercury poisoning, fetal alcohol syndrome, poor maternal nutrition or maternal diabetes, or maternal infection with toxoplasmosis or cytomegalovirus or rubella. This connection with Zika virus seems to be new and has not yet been proved, but it has been found in amniotic fluid and a study in northern Brazil found that all the mothers of the 35 microcephalic babies enrolled had been exposed to Zika virus and had had a rash or illness during pregnancy. Furthermore, the babies tested negative for other known causes of the condition. Spinal fluid samples are still being tested for Zika, but the US Centers for Disease Control is worried.
So is the US government. And the Canadian government…. and the governments of the 22 countries where Zika has recently appeared. Pregnant women are being advised not to travel to affected areas and the airlines are taking the warning seriously enough that they will allow pregnant women to change, cancel, or delay their trips without charge…. Ecuador, El Salvador, Jamaica, and Colombia have advised their female residents to delay planned pregnancies until at least next year, although the lack of access to contraception and safe, legal abortion in these areas make these suggestions unrealistic. Furthermore, it is estimated that at least half of pregnancies in El Salvador, for example, are unplanned or the result of sexual violence. In any case, microcephaly cannot be detected in a fetus until the second trimester (after 12 weeks), and second trimester abortions are more difficult and dangerous than earlier procedures.
Toronto, where I live, is surrounded by trees and water, and we have a huge mosquito population in spite of efforts to fight West Nile virus. I’m concerned, because I spend as much time as possible outdoors and mosquitoes seem to find me attractive. If you can’t avoid being around mosquitoes, no matter which diseases they carry, there are precautions you can take. Insect repellent is your first line of defence and it’s safe for pregnant women. If you are wearing it and sunscreen, put on the sunscreen first. Long sleeves and long pants, with cuffs to prevent insects crawling inside, will help and you can get clothing permeated with insect repellent. Wear light colours: mosquitoes like dark shades. Mosquitoes like standing water and cedar forests, so be prepared if you are around these. In Canada, mosquitoes are most active at dawn and dusk, and they can smell strong scents like shampoo and cologne, so it’s easier for them to find you if they can smell you. However, they can detect the carbon dioxide that you breathe out and they can sense your heartbeat, so it might not make much difference….
Once you’ve been bitten, tea tree oil can help the itch, as can a gel like After Bite. And folk wisdom, believed by children everywhere, says that if you make a cross on the bite with your fingernail, it will take the itch away. It does…. but only if you believe!