Longitudinal variation of the sensitivity of IgM assays in the first seven days after fever onset.

<p>1a: overall sensitivity based on samples collected from first and second chikungunya fever outbreaks in January and May to September 2008, respectively; 1b: sensitivity based on samples collected from the first outbreak due to CHIKV-A226 strain; 1c: sensitivity based on samples collected from the second outbreak due to CHIKV-226V strain. The numbers in brackets along the x-axis represent the number of samples tested for each day after onset of fever.</p>