Dengue virus (JVI cover)Last week I talked about evolution of HIV during transmission, and I was going to talk further about evolution of Dengue virus among schoolchildren1 as an interesting contrast to HIV.

The authors measured Dengue virus sequences over time in particular school districts in an endemic region, and I  entertained myself with an analogy between school districts for Dengue, and individuals for HIV, as pools in which virus circulated and evolved, and from which  viruses flung forth tentacles in attempts to spread. Dengue behaves very differently than HIV — the latter undergoes continuous, extensive evolution in situ, whereas it turned out that in the case of Dengue virus, microevolution within the school district is not very extensive — and I thought it might be interesting to ask why they are so different.

But on further contemplation I decided that (as is often the case with facile analogies) the situations are really not all that similar, and I don’t know that either case informs the other in any particularly useful way.

The critical difference is that in the case of Dengue sequence variation is dominated by virus migration into and out of the school districts:

… we observed little evolutionary change in those viral isolates sampled over multiple time points within individual schools, indicating a low rate of mutation fixation. These results suggest that frequent viral migration into Kamphaeng Phet, coupled with population (school) subdivision, shapes the genetic diversity of DENV on a local scale, more so than in situ evolution within school catchment areas.

Dengue virus (False colour)That’s not to say that the comparison is completely wrong; there may be a unit (whether within an individual, or within a certain geographically or socially-restricted unit somewhere) in which Dengue microevolution is an important contributer to persistence or transmission between units. But this paper doesn’t seem to have caught that unit, so I don’t think there’s much to really dig into.

In any case, there’s a paper, just become available in its online version, that’s much more interesting, and that strongly supports a speculation I made just about a month ago; so I’ll talk about that  in a day or two instead.

  1. Jarman RG, Holmes EC, Rodpradit P, Klungthong C, Gibbons RV, Nisalak A, Rothman AL, Libraty DH, Ennis FA, Mammen MPJ et al. (2008) Microevolution of Dengue viruses circulating among primary school children in Kamphaeng Phet, Thailand. J Virol 82:5494-5500. doi:10.1128/JVI.02728-07[]