West Nile virus infections in Romania after the 2010 outbreak - a retrospective study in human and animal population

Abstract

In this study the authors have made a retrospective analysis of West Nile virus infection in human and animals after 2010. Few studies have dealt with this arbovirosis in the last years and there is no analysis to correlate the evolution in animals and humans. To date it is considered that the largest outbreak of West Nile virus (WNV) encephalitis from Europe was registered in 1996 in Romania. Cases of encephalitis with WNV have been reported in our country before first in 1955 in Transylvania, followed by an outbreak in 1964 in Banat. The outbreak from 1996, ended with over 390 confirmed cases of encephalitis in humans the majority being registered in Bucharest and in the southern area of Romania. The epidemiological situation, after the implementation of a surveillance system for WNV in humans until 2010, was characterized by sporadic cases, WNV being reported yearly, except 2002. The infections were reported mostly in the south and south eastern area of the country. The age distribution in human cases recorded a majority in the group age over 65 years due to the senescence of the immune system and the associated diseases. The gender ratio was dominant for men, considering the occupational factor. In 2010 the second large outbreak of WNV was recorded and 47 confirmed cases of WNV infection were registered. After 2010, WNV encephalitis was recorded yearly and the area of detection was confined to eastern area and slowly to the to the whole country. Human cases were registered yearly in areas where the virus was detected in animals by serological screening. Considering the analyzed data, we can state that the main feature of WNV infection is the continuous virus spreading over the territory both in humans and animals. This can be determined by the climatic changes, that allow the surviving and multiplication of the competent vectors in new areas and maybe of the changes in the migratory routes of the birds- main amplifying hosts. Unfortunately, no statistical correlation between human and animal cases could be made. We can state that WNV is continuing to represent a threat for public health and more in depth research has to be made in order to characterize the evolution of the infection in our country and the causes of its endemisation.