We have found that the cytokines investigated had one of two immunologically important profiles during CHIKV disease onset and convalescence; furthermore, CXCL10 and CXCL9 were makers of disease severity. By identifying the immune profiles, we have created a clearer clinical picture of CHIKV disease. Importantly, further investigation is needed to correlate these profiles with disease onset and progression to use the cytokine profiles as biomarkers for severity and symptom persistence. The data presented here suggest that with further investigation, immunomodulators may significantly enhance patient recovery. The Failure of R (0) The basic reproductive ratio, R (0), is one of the fundamental concepts in mathematical biology. It is a threshold parameter, intended to quantify the spread of disease by estimating the average number of secondary infections in a wholly susceptible population, giving an indication of the invasion strength of an epidemic: if R (0) < 1, the disease dies out, whereas if R (0) > 1, the disease persists. R (0) has been widely used as a measure of disease strength to estimate the effectiveness of control measures and to form the backbone of disease-management policy. However, in almost every aspect that matters, R (0) is flawed. Diseases can persist with R (0) < 1, while diseases with R (0) > 1 can die out. We show that the same model of malaria gives many different values of R (0), depending on the method used, with the sole common property that they have a threshold at 1. We also survey estimated values of R (0) for a variety of diseases, and examine some of the alternatives that have been proposed. If R (0) is to be used, it must be accompanied by caveats about the method of calculation, underlying model assumptions and evidence that it is actually a threshold. Otherwise, the concept is meaningless. The basic reproductive ratio-also known as the basic reproductive number, the basic reproduction number, the control reproduction number, or R 0 -is one of the foremost concepts in epidemiology [1] [2] [3] . R 0 is the most widely used epidemiological measurement of the transmission potential in a given population [4] . It is a measure of initial disease spread, such that if R 0 > 1, then the disease can invade an otherwise susceptible population and hence persist, whereas if R 0 < 1, the disease cannot successfully invade and will die out. The concept is defined as the number of secondary infections produced by a single infectious individual in an otherwise susceptible population [5] .