The number of new cases of seasonal influenza in Europe continues to edge upwards, according to health protection authorities.
The European Centre for Disease Prevention and Control (ECDC) says flu viruses have been slowly spreading across the continent throughout the winter season, with the number of confirmed cases rising since the beginning of December 2011.
However, the overall rate of reported cases is still rated as “low” in 23 of the 27 EU countries included in the agency’s latest flu surveillance paper.
Bulgaria, Iceland, Italy and Spain recorded higher rates of flu but these are still well within the range of what is expected during the height of flu season, according to the ECDC.
A moving target
There are several strains of the influenza virus circulating and causing illness in different regions throughout the year. The virus is constantly changing so our immune system must first recognize this new virus before mounting a defense. Therefore each year there is a different level of public health impact from one year to the next.
Each flu season a network of experts collaborates on what they expect to be the three most common forms of flu virus circulating in the coming winter season. The strains identified by these experts make up the that years seasonal influenza vaccine.
This year, so far, the dominant flu viruses are the A/H3N2 viruses and, to a lesser extent, the A/H1N1 virus which was responsible for the 2009 global flu pandemic.
Last year the number of new cases of influenza in Europe tapered off near the end of April, leading the ECDC to declare the end of the flu season in early May.