A mathematical model to detect influenza epidemics
Cristina G. Pedraz/DICYT Researchers at the Red Centinela Sanitaria de Castilla y León (Spain) have developed an epidemiological model that allows early detection of influenza epidemics. The study, published in Influenza and Other Respiratory Viruses, was led by two experts from the Dirección General de Salud Pública (public health management in Castile and León): Tomás Vega and José Lozano, who have worked hand in hand with five authors from other countries. The mathematical model has been assessed and implemented by the European Center for Disease Prevention and Control (ECDC) and the World Health Organization Regional Office for Europe (WHO/Europe).
Although mathematically complex, this model is based “on the simple idea of moving influenza epidemic waves, aligning them in a single position and establishing a curve in order to calculate duration, baseline levels and average intensity”, the researchers state. Moreover, once the model is developed comparisons among seasons can be made in the same area or in different countries. Nevertheless, the most important is going to be “its ability to detect in real time the appearance of an epidemic in the monitoring process in all European countries”.
The researchers analyzed influenza and acute respiratory infections historical data from 20 European countries and collected week-by-week incidence of 5-15 years. Using this information, a model for each country was created, establishing the epidemic threshold and typical intensity by seasonal epidemics.
The study confirms that the intensity of the 2009-2010 influenza pandemic was “moderate” in Europe, with influenza activity at the top periods below confidence limit of 90% establishing the epidemic’s highest level. Notwithstanding, as the researchers explain, “the model would had been able to detect that pandemic during its first week in most of the countries and would only had produced some false alert on a third of involved countries”.
In this regard, the Consejería de Sanidad (a Spanish public health body) recently signed an agreement with WHO/Europe to develop new applications for this model. The research team at the Dirección General de Salud Pública (WHO consultant) coordinates an international working group to analyze intensity indicators, spreading, trends, dominant virus and impact of influenza epidemics in Europe, the region set to “immediately” put the method into practice.
The authors also highlight this model’s potential to study and model the epidemic behavior of other seasonal epidemics.
Relevance of the Study
According to the researchers, respiratory infections caused by influenza “increase the number of medical consultations and they are a major global cause of hospital admissions and mortality”. Even if influenza rates are higher in children, mortality associated with the disease is higher in older patients and in people with other conditions. Consequently, “influenza largely affects human health and it is a major challenge for health care services, so it is important to give precedence to monitoring to set priorities and efforts regarding prevention and control”.
The bodies responsible for the surveillance of influenza are to supervise annual epidemics and to detect and characterize current viruses. Additionally, early detection of seasonal epidemics “is of vital importance in order to alert health care services to mitigate morbidity, mortality and financial costs”. Furthermore, outbreaks in 1997 (avian influenza) and in 2010 (influenza A H1N1) “have lead to more efforts by international organizations and national public health authorities to improve and develop monitoring systems to perform accurate estimates of the dynamics of influenza at the local and national level”.