If we are able to use diagnostic tests to determine whether individuals who do not show symptoms are susceptible or are instead infected but not showing symptoms, we’ll be in a better position to estimate the chance of a major outbreak.
- Nik Cunniffe
The finding emphasises the need to develop and deploy reliable diagnostic tests to detect infected individuals whether or not they are showing symptoms, say the researchers.
Emerging epidemics pose a significant threat to human health worldwide. A principal challenge in infectious disease epidemiology is accurately forecasting the threats posed by diseases early in emerging outbreaks. Accurate real-time forecasts of whether or not initial reports of cases of disease will be followed by a major outbreak – an epidemic in which large numbers of people become infected – are necessary to determine which control measures should be deployed.
For all infectious diseases, there is a delay between infection and the appearance of symptoms, known as the ‘incubation period’, during which infected individuals are classed as ‘presymptomatic’. The incubation period, say researchers from the Department of Plant Sciences at Cambridge, can drive significant uncertainty in forecasting during the earliest stages of epidemics.
In research funded by the Biotechnology and Biological Sciences Research Council, the team used mathematical modelling to evaluate the effect of presymptomatic infection on predictions of major epidemics, choosing the Ebola virus as a case study. Their results, published today in the online journal PLOS Computational Biology, show for the first time that precise estimates of the current number of infected individuals – and consequently the chance of a major outbreak in the future – cannot be inferred from data based on symptomatic cases alone. This is the case even if factors such as the average infection rate and the death or recovery rates of individuals in the population can be estimated accurately.
Read the full story
Image: Ultra-violet screening for potentially Ebola-carrying liquids (cropped)
Credit: DFID - UK Department for International Development
Reproduced courtesy of the University of Cambridge
_____________________________________________