2013 Meeting of the American Society of Tropical Medicine and Hygiene
I just returned from this year’s meeting of the American Society of Tropical Medicine and Hygiene (ASTMH). For us in the developing country health world, it’s the biggest meeting of the year.. yet surprisingly small. Once you go to a few, you quickly realize you know just about everyone there.
Unfortunately, because I was preoccupied with a crushing NSF deadline, I didn’t get to see many of the presentations. I did, however, get to see many of the great people I know and, despite the deadline pressures, managed to have a great time.
Some highlights (for the layman), though:
1. Nipah virus: This one’s a beast. With a 70% case fatality rate (7 out of 10 people who become infected die), contact with this bug will pretty much assure there’s no tomorrow. Fruit bats area known reservoir though they seem unaffected by the virus. They urinate on pigs who transmit it to humans.
Sometimes, the bats urinate in certain tree sap collection buckets. People drink it directly, fall ill and then transmit to their families and kill them, too.
Because of Nipah’s ubiquity in fruit bats, the ease of isolating and producing stocks of the pathogen and it’s potential for major public health damage, the CDC has listed the virus as a Class C bioterror agent. Wow.
2. Imported zoonotic pathogens: More than 200 transmissible pathogens have been known to be imported into the US via the illegal wildlife trade. Remember, that most living things are mini-ecologies of bacteria, virae and fungi (yes, you too). Those people with the exotic snakes they imported in their bag? They brought more than snakes.
3. Plasmodium vivax (one of the four species of malaria parasites) relapses occur, on average, 14 months later. I found it interesting that it wasn’t 12. My mental transmission model confirmed that a 14 month relapse cycle would be much more suited to sustaining the pathogen than a more predictable 4, 6 or 12 month cycle. I will have to confirm with real (not fantasy) math, though. As vivax is a cold weather malaria, it makes a huge difference. Mosquitoes aren’t nearly as active in the winter.
It turns out, though, that I’m wrong, or misread the presentation (See Update below).
4. Nets with holes might be just as effective as nets without holes. We can stop collecting all those old nets and setting them on fire, now.
5. No one can agree on what dose of Primaquine to use during mass drug administrations to eliminate malaria. It’s kind of important. People with a particular genetic deficiency react badly to the drug, i.e. their red blood cells explode and they sometimes die.
6. A vaccine for malaria is on the way. It’s like the “check’s in the mail” for several decades. You can’t fault anyone for trying. We need one badly.
7. The Burma Restaurant in Washington, DC is truly fantastic, particularly the green tea salad, which tastes nothing like one would expect.
Outside of that, it was great to see friends. I can’t wait to see them again.
A friend wrote me to correct me on the timing of a relapse of P. vivax (and I appreciate it). Actually, it turns out he wrote a paper on it:
“Here: The Plasmodium vivax that was once prevalent in temperate climatic zones typically had an interval between primary infection and first relapse of 7-10 months, whereas in tropical areas P.vivax infections relapse frequently at intervals of 3-6 weeks. Defining the epidemiology of these two phenotypes from temporal patterns of illness in endemic areas is difficult or impossible, particularly if they overlap.”
Here: Tropical P. vivax relapses at three week intervals if rapidly eliminated anti-malarials are given for treatment, whereas in temperate regions and parts of the sub-tropics P. vivax infections are characterized either by a long incubation or a long-latency period between illness and relapse – in both cases approximating 8-10 months.
And Here: Median relapse times for malaria caused by Old World parasites (tropical, 4.5 weeks [95% CI 3.6–5.4]; temperate, 8.5 weeks [95% CI 6.8–10.3]) were shorter than those for malaria caused by New World parasites (tropical, 27.5 weeks [95% CI 21.6–33.5]; temperate, 34.0 weeks [95% CI 32.0–36.0]). In addition, in both hemispheres, median relapse times for infections caused by tropical strains were shorter than those for infections caused by corresponding temperate strains, although this difference was not significant in the New World (Figure 3). The 95th percentile relapse times for the strain categories follow: Old World tropical, 9.5 weeks (95% CI 5.4–13.5); New World tropical, 40.3 weeks (95% CI 34.4–46.3); Old World temperate, 30.9 weeks (95% CI 19.9–41.9); and New World temperate, 97.7 weeks (95% CI 97.6–97.8). The HRs from the survival models (adjusted for neurologic treatment) follow: Old World tropical, 39.6 (95% CI 9.2–171.0; p<0.001); New World tropical, 0.93 (95% CI 0.36–2.41; p = 0.89); Old World temperate, 3.1 (95% CI 2.2–4.6; p<0.001)—all relative to New World temperate (reference).