|My new stove and the view out back of our rent house|
From my kitchen window I can look out back over the Moei river, which marks the international border between Myanmar and Thailand. Down one end of my block is an international border crossing and down the other is the malaria clinic. While I’ve been working on my Thai, it does me little good in this neighborhood since most of my neighbors are Karen and they seem to know very little Thai.
|Across the Moei River from Tha Song Yang|
Across the river there appears to be a simple mosque. We can’t really see it, but there are several wooden, thatch roof structures and we hear the call to prayer several times during the day. The river here is sandwiched by mountains on both sides and the resulting canyon makes a perfect echo chamber for carrying the sounds of the Imam’s song. I don’t know whether the moslem adherents there/here are mostly Karen or if they are Rohingya who are attempting to flee persecution from the other side of Myanmar. I do know that some of the Rohingya have been making their way to the refugee camps, one of which (Mae La, with about 50,000 people living in it) is a few miles south of here.
|A river ferry transporting someone across a very high Moei River|
Over the last several days I’ve been struck by some interesting realities, a few that are related to research areas that I hope to investigate while here. The most obvious to my family and me has been the openness of households…
Mosquitoes are most apparent at dusk and dawn, but if they get into your dwelling they’ll feed during the night too. My toes and feet have been pretty thoroughly gnawed. I brought a mosquito net for my son’s bed, and we’ve all been using some repellant from Mahidol University which appears to be made from lemongrass, but I’ve yet to find a net that will work for our own bed. Furthermore, almost every house has openings that aren’t covered. The tops of the walls in our bathroom and kitchen areas have ventilation holes large enough for me to stick my arm through – a feature which actually makes the humid bathroom and kitchen bearable in the humid heat.
Such openings also make it quite easy for mosquitoes and other creatures to move into the house at will. Last night we were awakened by a Tokay gecko, probably close to a foot long, that appears to have worked his way in as well. If you’ve never heard a Tokay gecko’s call before, it isn’t something that is easy to ignore. My son and I decided to name him Figaro, being that he so loves to sing.
There has been some question about whether or not malaria transmission here occurs within households or outdoors, perhaps in agricultural fields. For one species, Plasmodium vivax, infections appear to cluster in younger children. I take this as potential evidence of exposure in or around the household, with older household members probably still being infected but having some acquired tolerance for vivax infections.
Last night as I sat out front of my house, drinking a sweaty Chang beer, listening to the call to prayer and the rain that hasn’t stopped now for close to 3 days, I looked down the street and saw almost every household with doors and windows wide open, families sitting inside enjoying each other’s company. If transmission is occurring within households, it’s going to be near impossible to completely stop. I’m fortunate to have a relatively well built structure to stay in while living here and I can’t keep the mosquitoes out. It is more than a little overwhelming to think about the options for the countless others who aren’t as well off as a poor graduate student.
But even if exposure occurs outside of the household, and I think that for Plasmodium falciparum it does, it will be at least as hard to halt transmission. Children cannot stay inside their beds or houses forever, it is healthy that they run and play outdoors. Parents need to tend their agricultural fields, to hunt and fish, so that they can put food on the table.
Another thing that has become blatantly clear is the effect of the rain on everyday life. As I write this I believe it has been raining almost non-stop for about 2 ½ days. The rains don’t make life come to a stand-still, but they do make things more difficult and uncomfortable. The market was still open early this morning. The steady stream of Karen migrants walking down our street continues. A few hours ago I walked down to the border patrol check station, where migrants check in, and found empty, closed buildings (it is Sunday here) and a few boat drivers ferrying people to and from Myanmar from the Thai side of the border. One jokingly asked if I’d like a ride across the river (and as exciting as that might be, it’s probably a bad idea). When the Karen here were still at war with the Burmese military, fighting mainly occurred during the dry season – it is too difficult to traverse the countryside during the wet season.
I frequently find heterogeneities in life to be fascinating fodder for research and theory. Many of the statistical and mathematical models that population scientists, demographers, and epidemiologists use assume homogeneity in whatever processes we are studying: random mating, random mixing, random contacts, etc. I think we all know that these things aren’t realities, but frequently that fact gets lost in the simple assumptions that are made, sometimes out of necessity, in research.
Here I find some interesting heterogeneities in the rainy season. While I complain that it has basically rained for several days straight, at times the rain slows. During those times, traffic on the streets picks up. This isn’t surprising, wading through puddles of muddy water isn’t fun. Though the countless motorcycle drivers around here are quite adept at driving one-handed while holding an umbrella in the other hand, I imagine they’d much rather the rain stop altogether as well.
And with the rains here comes malaria. Tak Province consistently reports the highest number of malaria cases (both vivax and falciparum) of any province in the Kingdom, and within Tak Province, Tha Song Yang District has the heaviest malaria burden. Cases here are highly seasonal, with only a very few in the dry season. However, the trickle of infected people at the local malaria clinic isn’t a steady flow throughout the rainy season. I once fancied a Poisson process of arrivals at the clinic, but this too doesn’t appear to be the pattern. What is a pattern, however, is that after a rain, the clinic is quite busy. (The clinic is closed on weekends and so Monday morning is generally a busy time too). Does this mean that no one feels sick while it’s raining?? Probably not. Also, it takes approximately 2 weeks from the time of infection until a person actually feels classic malaria symptoms. So rain can lead to increased mosquito vector populations but infections that have occurred in the last day or two aren’t likely to be symptomatic so quickly. No, it appears that people who are sick would rather not wade through muddy water, potentially have to illegally cross an international border, and then make their way down to the waiting area of a clinic during a torrential downpour.
I think this makes perfect sense, but it doesn’t wind up in any model of seasonality in malaria infections that I’ve ever seen. Rains = more mosquitoes = more malaria. But rains also mean that people are likely to at least momentarily delay seeking treatment. Infected people who wait longer before seeking treatment are important in malaria epidemiology because they spend longer amounts of time being infectious – potentially acting as so-called “super spreaders” (individuals who spread infectious disease at higher rates than do others).