Dengue epidemiology in South Vietnam.

<p>The total annual number of dengue cases (blue bars) and relative serotype prevalence (lines) over the period 1994–2008 in the southern 20 provinces of Viet Nam show the characteristic fluctuation in disease incidence and sequential replacements of dominant serotypes. Source of data: Vietnamese Ministry of Health Dengue passive surveillance scheme and kindly provided by the Pasteur Institute, HCMC, Viet Nam. The Hospital for Tropical Diseases is a tertiary referral hospital for infectious diseases.</p

Comparison of age structured dynamics between model (i) and model (ii).

<p>(a) The lines show the proportion of the population at each age (for model (i) (top) and model (ii) (bottom)) who have suffered one (solid dark blue line), two (solid red), three (solid green), four (solid magenta) and any (solid black) dengue infections. For model (ii) the proportion of the population that is at risk of disease (defined as having seen 1, 2 or 3 serotypes) is also plotted (dotted black) for comparison to the equivalent in model (i) (solid dark blue). Generally, in model (ii) people are exposed to dengue at an earlier age, experience heterologous infections younger, and take much longer to become completely immune. (b) For model (i) ((ii)), the blue (green) bar shows how the average age of disease (DHF), determined as heterologous infection, changes with the number of serotypes present whilst the small bars show the change in age of first infection. The increase in the total force of infection with the number of serotypes is shown as dotted lines (model (i): blue, and model (ii): green). (c) For model (i) (blue line) and model (ii) (green line) we observe that increasing acts to decrease the average age of first infection (here estimated as 1/total force of infection) and that for all levels of this value is significantly lower when allowing for third and fourth infection (model (ii)). Parameter values: ((a), (b) and (c)) and (a), (b).</p

Comparison of synchronisation and single-serotype dominance between model (i) (<i>top</i>) and model (ii) (<i>bottom</i>).

<p>(a) The synchronisation pattern between serotypes 1 and 2 indicates that, for both models, most of parameter space is characterised by desynchronised behaviour i.e. the dynamics of the two serotypes are not ‘locked’ together. (b) Using a measure of single serotype dominance (where 0 corresponds to at least two serotypes being simultaneously dominant and higher values indicate a greater tendency for one serotype to be dominating at any given time), one can observe that in both models the trend is for increasing levels of dominance with increasing enhancement; this trend is more pronounced in model (ii) than model (i).</p

Comparison of inter-epidemic period and serotype persistence between model (i) (<i>top</i>) and model (ii) (<i>bottom</i>).

<p>(a) As enhancement increases so too does the epidemic period observed in each model. There is also a trend towards longer periods at lower . However, these trends both appear to be stronger in model (ii). (b) The risk of stochastic extinction within the model is shown as the proportion of time in each model that the prevalence of a particular serotype exists above a specific threshold. In both models there is a low risk of extinction but the risk increases with enhancement; again, this trend is stronger in model (ii).</p

Supplementary Figure 2 from Antibody responses to avian influenza viruses in wild birds broaden with age

Change in HI titre for each antigen between 2007 and 2008 for each of the eleven birds that were sampled in both years

Supplementary Tables from Antibody responses to avian influenza viruses in wild birds broaden with age

Results of statistical analysi

Supplementary Figure 1 from Antibody responses to avian influenza viruses in wild birds broaden with age

Cumulative proportion of birds sampled during each sampling year and in the population