Special report: Several exotic mosquitoes have been making advances onto European soil and with them they often bring diseases that have been unknown in Europe before their arrival – the latest discovery is named the Usutu virus and was discovered in central Germany
At the end of August 2012, during an extensive blood sample test, the Usutu virus was found in one of the blood samples from a donor in Hessen, Germany. The Usutu virus is relatively new to the European Union as it is mostly found in Africa. It is extremely rare that the Usutu virus has been found in a blood sample of a person, as infection is not common in Europe. These kinds of exotic viruses are more often entering Europe given the effects of climate change, which is making it a more attractive feeding and breeding ground for these mosquitoes.
This discovery has been made by virologist Dr Jonas Schmidt-Chanasit from the Bernhard-Nocht-Institut for Tropical Medicine in Hamburg. Schmidt-Chanasit has stated that more research is needed before any conclusions can be made about this outbreak of the Usutu virus and is therefore asking doctors in Germany to send blood samples to the BNI in Hamburg for screening.
The Usutu virus can lead, in the worst case scenario, to acute inflammation of the brain. Symptoms can seem innocent, such as headache, fever, drowsiness, fatigue and confusion. Given that these symptoms are seemingly innocent, the virus can pass through the body without the person being aware of being infected. Additionally, it is quite important that this virus has been found specifically in a blood sample of a donor, given that these viruses can be transmitted via blood transfusions. These kinds of viruses are rare and therefore are not screened for in a regular blood test. And as such, this is a risk to the safety of blood supply.
The Usutu virus is not the first exotic virus to have entered Europe. Over the years there have been several outbreaks of similar viruses. In 2007 there was an outbreak in a northern region of Italy of the Chikugunya virus, which infected a few hundred people. Another virus, which is increasingly prevalent in Europe, is the West Nile virus. This virus is now emerging every summer in Eastern Europe, but is slowly moving towards Central Europe. Finally, the Dengue virus has been found in 2010 in regions such as south-east France, as well as Croatia and is also known to show up in Greece.
These examples all show the increase of emerging pathogens, which are new to the EU, and provide specific public health challenges. Coming back to the problem with blood transfusion, during the virus outbreak of the Chikugunya virus in Italy in 2007, the blood donation banks in the region had to be shut down because of a risk of infection. This protection measure actually caused a temporary shortage in the supply of blood and blood products in the region.
As can be seen by statistics from the European Centre for Disease Protection and Control the prevalence of exotic mosquitoes in Europe has increased in past years. There have been increased sightings of the yellow fever mosquito, primarily the Aedes aegypti
, the Asian tiger mosquito Aedes albopictus
, as well as other potentially dangerous vectors. These exotic mosquitoes can carry certain diseases, such as Dengue fever and others. The Usutu virus is also a vector-borne virus and in the same category. The virus is also a zoonosis, a disease that can affect several species, in this case with the possibility to infect humans.
The Usutu virus originates from Africa, where it was first discovered in South Africa in 1959 and since then it has been discovered in several other African countries. The first time this virus has been discovered outside of Africa was in 2001 in Vienna, Austria with blackbirds, with a peak in 2003, most probably because this was an exceptionally warm summer. The last two summers there have also been several incidents in the south of Germany where birds have died from the virus.
The first time the Usutu virus has been discovered in humans has been in 2009 in Italy, with two patients who had weakened immune systems. From what has been reported so far, this infection in Germany seems to be a new case, a person is or has been infected with the virus, without having a weakened immune system.
The warm summers are particularly important to mention, given that climate change has been mentioned as one of the causes for the increase in exotic mosquitoes in Europe. Research has been done in the past to confirm that the advance of these exotic mosquitoes in Europe is linked with the increase in temperature, as well as the increase in international trade. An example shows that stagnant water in truck tyres is an ideal environment for mosquitoes to breed and they therefore travel with the truck. Similarly, the mosquitoes travel via airplanes or trains as well.
The following map gives an overview of some of the mosquitoes and vector-borne viruses in the past five years in Europe.
As can be seen from the map there have been several emerging pathogens in Europe in the past five years. The areas where the emerging pathogens and the mosquitoes have been found have been quite far towards the west of Europe already. The discovery of the Usutu virus is an important development, as it shows the entry of yet another, potentially dangerous and exotic disease on European territory. The EU and the World Health Organisation are both monitoring this situation to make sure appropriate measures are taken, when needed.
Taking into account all the developments mentioned in this article, and if we assume that climate change will continue, these mosquitoes and their pathogens should be a growing concern for the EU to deal with. The EU has some competence in this field, particularly when dealing with blood policy, such as donor, and recipient, safety as well as the issue with blood supply, via the Blood Directive 2002/98/EC as well as the Decision on Cross-Border Health Threats, which is a current ongoing legislation to increase cooperation throughout the EU on health threats such as these vector-borne diseases and emerging pathogens.
Daphne van Doorn works for Rohde Public Policy, a public health and environment development consultancy, based in Brussels.