So, how worried should we be about those pesky mosquitoes that nibble on us while we enjoy the Sea to Sky outdoors?
Last week, news broke that Vancouver Coastal Health (VCH) Public Health and the BC Centre for Disease Control had launched a small-scale mosquito surveillance pilot project in the Sea to Sky region after four people became seriously ill from bites from the insects last year.
The four patients, who had all been in the Sea to Sky when they were bitten, contracted California Serogroup (CSG) viruses—specifically Snowshoe Hare Virus (SSHV) and Jamestown Canyon Virus (JCV)—and came down with encephalitis, which is a swelling of the brain.
The health authorities, with support from Líl̓wat Nation, Squamish Nation and the University of B.C., are undertaking the study to better understand the local mosquito population and the viruses they carry.
The Squamish Chief caught up with Dr. Moliehi Khaketla, Sea to Sky medical health officer with Vancouver Coastal Health to find out more.
What follows is a version of that conversation edited for length and clarity.
Q: Looking at the four people who became sick last year with encephalitis, was there any extra vulnerability in terms of age? Were there more children, adults or a mix who became ill?
A: When we talk about a small number, like four cases, particularly those that are localized within a small geographic area, for privacy reasons, we're very careful to be able to provide enough information, but not so much information that it risks potentially invading their privacy. So, we're providing a general description in that these are people who had spent time within the Sea to Sky region. And when we investigated further, we were able to ascertain from knowing when they would have likely acquired the infection based on their presentation, that they had spent a significant amount of time outdoors.
Q: I understand that. So, I guess the question is, should parents be more worried about kids, or should we be more worried about the elderly or adults?
A: The messaging that we're sending to the public is really targeted at the entire population, so from children all the way to adult populations, because this type of illness can impact young children as well as adults. There isn't a specific target population with this message, except for the entire population, really.
Q: In terms of the protection measures, which mosquito repellents are most effective?
A: There are a lot of different brands out there, people may be confused about what to pick or not, so there's good information on the HealthLinkBC website. In the list of ingredients, we generally look for DEET, specifically, which is effective in terms of an appropriate repellent of these mosquitoes.
For the little ones under the age of six months, obviously, any DEET containing product would not be appropriate, and so guardians should protect them while in strollers with netting, for example.
Q: We're a very active outdoor community. How concerned should we be about this?
A: Really, it is a balance. We know that being outdoors, being active, particularly within the beautiful Sea to Sky region, is so important for physical health as well as mental health and well-being. And so we encourage that. All we're saying from a public health perspective, based on the information that we know so far, is we just want people to be aware that as they're recreating outdoors to make sure that they're taking the appropriate precautions, particularly during those times when mosquitoes are most active during the summer months—from now until usually into October or so.
We don't want people to be alarmed and want to stay indoors.
It's just being practical and being aware and prevention, prevention, prevention. Not just in terms of insect repellent, but also things like wearing protective clothing, and I think particularly for people with little ones, if you're going for an evening walk, make sure you put that mosquito net over the baby stroller.
And then there’s doing some of the practical things around our homes, including making sure that we don't have standing water where mosquitoes could breed in our backyard. Making sure that we remember to put our screens on our windows. Things that prevent contact with mosquitoes, which may be carrying different types of viruses.
Q: Why was it a year before the public heard about this? A lot of us had mosquito bites already when the news came out.
A: It's a little bit of a complicated answer, because we actually did, at the time, make our health-care providers aware that this was something that we're starting to see. They knew that they needed to be thinking about it if they saw people presenting with an unusual presentation that may be linked to encounters with mosquitoes. So, that information did go out.
Then, following that, there did need to be a bit of co-ordination to ensure that we were well positioned to be able to have the pieces in place to study what was happening further.
The timing actually worked out well now that we were able to get all the partners together and then be able to have this plan for setting out the traps, have the labs co-ordinated. And then now, as the weather is getting warmer, this is a good time for us to be communicating this more broadly. I will add that since those cases were identified late last year, so far this year, we have not had any cases reported. So I think that helps put things into perspective as well.
Q: How extensive is the trapping and testing?
A: To determine where to put the traps, we relied on guidance from the communities. I mentioned the partnership that includes the Lil'wat Nation as well as the Squamish Nation. We relied on that local knowledge to help guide our placement of the trapping, but we also wanted to get a good range right across the corridor. And so we've targeted communities all the way from Pemberton to Squamish, where we've strategically placed these traps, to really get a good sense of where the mosquitoes are and to see if there's a difference between communities, for example, in terms of the counts.
That's just one aspect, and then the other aspect would be testing them, and then figuring out what species they are, as well as the different pathogens that they may be carrying. It's quite an interesting step-by-step process that we're following that'll give us a good sense right across the corridor about what's happening.
Q: And it's early days, I imagine? Have there been any infected mosquitoes tested already?
A: It is still early in the project. We're continuing right until the end of August, which is the peak mosquito time, and then following that, our partners with the expertise at the university, as well as the lab, will be doing that testing and then the counting, as well.
So, it'll be several months before we know more. And then, based on that information, that'll inform any additional communication that happens with the public about what's happening,
Q: Can you go over again what people should watch for in terms of symptoms of illness?
A: For most people who may get bitten and get infected, they may not even know it. It's usually a very mild illness, or they could have no symptoms at all, and then there'll be a proportion of people who get bitten, and within maybe five days or so of mosquito bites, up to about two weeks, they may develop a mild illness, and that could present a flu-like illness, where they have a fever or fatigue or headache, they may feel a bit nauseous and they may have some vomiting, and usually that'll last a few days, and then it'll resolve without any need for medical attention. And then, on the other end of the spectrum, a smaller proportion of patients may present with severe illness, typically presenting with neurological symptoms, indicating that there might be an infection within the brain.
And so those ones would be things like a severe headache that doesn't go away, a fever, neck stiffness, confusion, and not looking well. And then for children in particular, things like seizures can happen as well. And so those are the types of things that would be red flags that would warrant people seeking medical care.
Q: And these aren't new viruses, correct?
A: Yes, these are not new infections in the province. What prompted us to take a closer look was the number of cases that we saw within a short amount of time in the corridor, as well as the severity of illness that presented. So even though it was a small number—four is not a lot—if you look at going back a number of years, from 2009 until 2024, we had only had 10 cases reported in the province. And two of those had been within Vancouver Coastal Health. And so really it was the cluster within a short amount of time, and the severity of illness that prompted us to look into this further. But these are not new, not in B.C., and also not in Canada. There have been many, many reported cases, mostly in eastern provinces, but also in Alberta, Saskatchewan, most of Quebec and Ontario.
Q: Anything else you'd like us to stress that you've seen come up since the announcement went out that maybe isn't getting through to people?
A: This is just really a message for people to be aware and take precautions. If they do get sick, they should seek health care, similar to how they would with any other illness. And really, it's an exciting opportunity to learn about what is happening with the mosquito population within the corridor, and then once we know more, we'll be ready to share as well.
