The Zika Virus Explosion, A Perspective  – by Ray Hudson

Dr. Suni Boraston indicating the tropics as the Zika hot spot. Photo: Ray Hudson
Dr. Suni Boraston indicating the tropics as the Zika hot spot. Photo: Ray Hudson
Dr. Suni Boraston indicating the tropics as the Zika hot spot.
Photo: Ray Hudson

Just over two months ago, we spoke with ­­­­Dr. Suni Boraston, Director of the Vancouver Coastal Health Travel Clinic about precautions and vaccinations travellers should take while vacationing in the tropics.  One of the diseases she mentioned was the zika virus, a mild and short duration virus, related to dengue and yellow fever, but much less viralent.  On February 1, 2016, within two months of the earlier report, the zika virus was declared a public health emergency by the World Health Organization (WHO) following stories of babies, in Brazil, being born with underdeveloped heads, technical name: microcephaly.

Here’s some background:

The zika virus, was first identified in the forests of Uganda in 1947,  the first human infections reported in 1952.  Since that time there have been outbreaks reported across tropical Africa, Southeast Asia, the Pacific Islands, Central and South America, with some infections being reported in the Southern US, and now in China.  So far, there have been no reports of infections in India, however the country is on alert and preparing for what appears to be the inevitable.

The disease is spread by the bite of the Aedes mosquito, which becomes the vector (source of infection) by taking the blood of another individual infected with the zika virus.  This is the same mosquito that spreads the much nastier: dengue fever, also known as “break-bone fever,” yellow fever, and chikungunya (pronounced Chik-un-goon-ya) a Makonde word meaning “that which bends up.”

One important thing about the Aedes mosquito, is that it is active in the day. According to the WHO, the peak biting periods are early in the morning and in the evening before dusk, unlike the anopheles mosquito, which is the vector for malaria and is only active at night.

Adese (zika-bearing) mosquito
Adese (zika-bearing) mosquito

According to the Centre for Disease Control (CDC) the zika virus produces a much milder fever, headache, rash, joint pains, abdominal pain diarrhea and vomiting.  Usually the symptoms are mild and disappear on their own. Some people may not realize they’ve been infected at all.

We returned to the Vancouver Coastal Health’s Travel Clinic and spoke with Dr. Boraston about this dramatic shift in attention being brought on this seemingly weaker cousin and asked if the zika virus is as big a problem as it’s being presented, or is it a case of over-reporting.

“We don’t know that yet,” Dr. Boraston replied.  “The full answer is that we’ve been watching the zika virus for a number of years.  There was a big outbreak in French Polynesia in 2013, and it slowly spread across Central and South America.  Columbia had a huge outbreak about 18 months ago, but it was Brazil’s outbreak that alerted us to an increase in microcephaly, babies born with a reduced head size. It was Brazil that tweaked to that, but at the same time Brazil had also done some things that increased their reporting of microcephaly. They changed the definition of microcephaly and they made it a reportable disease.”  Those are what are called confounders.

Dr. Boraston said she had no doubt that there is a link between the zika virus and microcephaly, but added that they don’t know how much yet.

“There is a biologic basis for this,” Dr. Boraston said. “If a pregnant woman is infected with rubella, toxoplasmosis, or cytomegalovirus, the baby can have microcephaly. But the number of cases that Brazil was reporting was huge, something like four thousand new cases from October 2015 to January 2016.  It’s a suspiciously high number. So they looked at French Polynesia again, and they did report an increase in microcephaly over the time of the zika outbreak; 78 cases more than expected.”

She said that the process will be repeated in Columbia to see if they had an increase, and then they’ll go back and look at what was actually happening in Brazil.

“So I don’t think it’s as scary as the media is making it,” Dr. Boraston said,  “but there’s no doubt that if you’re a pregnant woman going down to one of those areas, you should think twice about it. We’re telling women who are bound and determined to go, to use insect precautions.  Pregnant women can safely use repellants, long sleeves, long pants, no perfumes.”

With respect to repellents, Dr. Borston said the most effective products contain an unpronounceable chemical compound known as DEET.

“DEET is safe,” she replied to a question about its safety. “The only people who got into trouble with DEET were infants where it was overused. They had some reversible neurological issues. But it’s safe for children and adults who use it properly.”

There has been some confusion about how long women may be at risk following exposure. The countries, where zika is endemic, are saying women should wait two years before they get pregnant. However, this advice is directed at women living in endemic areas.  The additional time period provides an opportunity to get the outbreak under control.

“For women who want to travel to zika areas,” Dr. Boraston said, “we suggeset they wait two months after being in a zika area before trying to get pregnant. I think that two months is overkill for women. We know this is a very quick disease.  It’s got a short incubation period,  and once it’s gone, it’s done and gone.”  Men? Who knows? There have been a number of cases where the zika virus has been found in semen and in some cases transmitted it to sexual partners, in one case, they found the virus in semen 62 days after the original infection. As a result, men are being told to wait two months before having unprotected sex, and if the traveller has a pregnant partner at home, he shouldn’t have unprotected sex for the duration of the pregnancy.”

Another wrinkle in the zika story is that it appears to be linked to Guillain-Barre syndrome (GBS).

“The French Polynesian outbreak showed that there does seem to be a greater incidence of GBS,” said Boraston, “but there was only a slightly higher increase to what they were expecting.”

GBS is a neurological illness that can cause major fatigue and muscle wasting. You can end up in an ICU on a respirator for the duration of the illness, but it is reversible.  You can also get GBS from influenza and campylobacter, which is like a bad food poisoning.

Asked about the development of a vaccine, Dr Boraston said that researchers are working on it. She said they have just developed a vaccine against dengue fever, for use in endemic countries like Mexico, Brazil and the Philippines, and expect they might be able to use the same technology in developing the zika vaccine. They are hoping to have it out in eighteen months.

Zika is certainly a disease to be understood and respected, however Malaria continues to be the most efficient killer around the world.  In 2015 (according to the WHO), there were 214 million cases of malaria resulting in an estimated 430,000 deaths.

With climate warming, is there any concern with zika moving north? The southern United States already has the right mosquito for zika, but Dr. Boraston doesn’t think it will move north.

“We don’t have the vector (mosquito) here despite the legendary voraciousness of mosquitoes in Canada,” said Dr. Boraston. “Could they become carriers for this virus?  I just read that they are doing the studies to determine if that very thing is a possibility, but I doubt that it would find the northern mosquitoes a very efficient vector. The West Nile virus never really got a hold here. It gets too cold and the virus couldn’t survive that.”

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