Quantification of the severity of an outbreak in human infection control

BACKGROUND: The severity of an outbreak is a priority in decision-making for human infection control. However, there have been no reports on how to quantify the severity of an outbreak. METHODS: We propose a simple method to measure the severity of an infectious disease outbreak. It involves scoring the severity of clinical signs, the transmission of the infection, the number of cases, and the infection source. RESULTS: The method was evaluated using the data available at the early stage of some recent outbreaks of infectious diseases, including the influenza A (H1N1) pandemic in 2009, and the evaluation supports the design idea. CONCLUSION: The method is practical for rating the severity of an infectious disease outbreak, though it should be optimized. It could also be used to judge whether an event constitutes a public health emergency of international concern (PHEIC) or not.