Assessing the danger of self-sustained HIV epidemics in heterosexuals by population based phylogenetic cluster analysis. eLife
In epidemiology, the “basic reproductive number” describes how efficiently a disease is transmitted, and represents the average number of new infections that an infected individual causes. If this number is less than one, many people do not infect anybody and hence the transmission chains die out. On the other hand, if the basic reproductive number is larger than one, an infected person infects on average more than one new individual, which leads to the virus or bacteria spreading in a self-sustained way.
Turk et al. developed a method to estimate the basic reproductive number using the genetic sequences of HIV to investigate how efficiently HIV spreads among Swiss heterosexuals. They found, that the R0 for Swiss heterosexuals is estimated to be 0:44 (95%-confidence interval 0:42—0:46) and it is decreasing by 11% per 10 years (4%-17%). Furthermore, the basic reproductive number differs by subtype of the HIV virus, indicating that the geographical region where the infection was acquired may play a role in transmission. The authors found that people who are diagnosed later or who often have sex with occasional partners spread the virus more efficiently.
In conclusion, the findings indicate rather diminishing HIV transmission among Swiss heterosexuals far below the epidemic threshold. The approach allows to assess the danger of self-sustained epidemics from any viral sequence data. Furthermore, the method can help HIV epidemics to be monitored at high resolution using sequence data, assesses the success of currently implemented preventive measures, and helps to target subgroups who are at higher risk of an infection – for instance, by supporting frequent HIV testing of these people.
Additional comment Dr. Dominique Braun and Prof. Huldrych Günthard
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