9 August 2011

Risk of mosquito-borne disease: advice for travellers to Europe and neighbouring countries

Europe has several native mosquito species capable of transmitting disease (e.g. Anopheles and Culex spp).  In recent years, due largely to the effects of climate change and increased global travel and trade, populations of other exotic mosquito species (e.g. Aedes spp) have become established in the region. The presence of these species increases the risk of locally acquired mosquito-borne diseases, previously never or rarely seen in Europe, occurring following importation from endemic countries [1]. Travellers may be at risk of these diseases which include:

Chikungunya virus

Chikungunya (CHIKV) is a viral infection of humans and non-human primates transmitted by Aedes spp. mosquitoes. CHIKV is an emerging disease in parts of southern Europe and is endemic in parts of sub-Saharan Africa, the islands of the Indian Ocean, and South and South East Asia.

Between July and September 2007, the first locally acquired cases of CHIKV to occur in Europe were recorded in two contiguous villages in North Eastern Italy. The presumed index case was a local resident who developed a febrile illness shortly after returning from India to one of the villages in June 2007.  There were 205 locally acquired cases with one death during the outbreak [2].

In 2010, two locally acquired cases of CHIKV and four imported cases occurred in the Var Department, Provence Alpes Azur region of France [3]. As of 4 August 2011, one imported case of CHIKV has been confirmed in Provence Alpes Azur region; there have been no cases of CHIKV in mainland France so far in 2011 [4]. Mosquito surveillance in the region has been strengthened and vector control measures have been implemented [4].


Dengue is a viral infection of humans transmitted by the Aedes spp. mosquito. Infections can be asymptomatic or can vary in severity from very mild symptoms to very severe illness with neurologic and haemorrhagic manifestations.

In September 2010, two cases of locally acquired dengue were reported in Nice (Alpes-Maritimes Department, Provence Alpes Azur region) France. These were the first cases to be reported in mainland France [3]. As of 4 August 2011, eight imported cases of dengue have been confirmed in Provence Alpes Azur; there have been no cases of dengue in the region so far in 2011 [4]. Mosquito surveillance in the region has been strengthened and vector control measures have been implemented [4].

In September 2010, a German tourist developed dengue shortly after returning from a holiday on the Pelješac peninsula and the island of Korcula in Croatia. He had not travelled elsewhere and it was presumed the illness was acquired in Croatia. In October 2010, a second case of locally acquired dengue was reported in woman resident in the same area, who had not travelled outside Croatia [5]. There have been no cases of dengue reported in Croatia in 2011 [4].



Dirofilarial infection is a parasitic disease in which larval worms (microfilaria) are transmitted from dogs or cats to humans by the bite of an infective mosquito (usually Aedes or Culex spp.). Infection in humans can vary in severity from asymptomatic to severe. In Europe, human Dirofilaria infections are caused mainly by Dirofilaria repens and are characterised by subcutaneous larval worm nodules near the point of the mosquito bite, or localisation of the parasite to the eye (e.g. orbit, eyelid, subconjunctiva, and vitreous humour). Dirofilaria sp. have also been shown to infect viscera (lungs, heart and mesentery) as well as female breast and male genitalia.

Dirofilarial infection is an emerging zoonosis in parts of Europe including France, Hungary, Italy and Russia, with small numbers of human cases reported annually [6]. As of 2 August, two confirmed human cases were reported in Latvia, the first reports of human dirofilarial infection in the country [7].


West Nile Virus

West Nile Virus (WNV) is a viral illness of humans and birds transmitted by Culex spp mosquitoes.  Human infections can be asymptomatic or can vary in severity from very mild symptoms to neurological illness including meningitis or encephalitis.

Outbreaks and intermittent cases of human WNV infection have occurred in Europe since the 1950s. Countries involved include Albania, Austria, Belarus, Bosnia, Bulgaria, Croatia, the Czech Republic, France, Greece, Hungary, Italy, Kosovo, Moldova, Montenegro, Portugal, Romania, the Russian Federation, Serbia, Slovakia, Spain and the Ukraine [8].

The first human cases of WNV in Greece for many decades were reported in 2010 with 262 cases and 25 deaths [9].  As of 3 August 2011, six laboratory confirmed cases of WNV have been reported from the regions of Karditsa (two), Larisa (three), Thessaloniki (one) in Greece; a further laboratory confirmed case has been reported from an unspecified region [10].  As of 2 August 2011, human cases have been confirmed in Romania (one) and the Russian Federation (four) [11].  A map of reported cases during 2011 in the European Union and neighbouring countries is available on the European Centres of Disease Prevention and Control website.

Advice for travellers

Each of these diseases is transmitted to humans by the bite of a mosquito. Practising insect bite avoidance measures will reduce the risk of travellers acquiring a mosquito-borne disease. Travellers should be aware that Aedes spp mosquitoes bite during daylight hours, while Anopheles and Culex spp mosquitoes bite during the evening and night.

Advice for health professionals – the returned traveller

Health professionals should be alert to the possibility of a mosquito-borne disease when consulting with an ill-returned traveller from Europe or neighbouring countries [12].


1. European Centre for Disease Prevention and Control. Public health importance of the invasive mosquitoes of Europe. January 2010. [Accessed 9 August 2011]. Available at:




2. Rezza G, Nicoletti L, Angelini R et al. Infection with chikungunya virus in Italy: an outbreak in a temperate region. Lancet 2007; 370: 1840–46

3. Institut de Veille Sanitaire. Dispositif de surveillance du chikungunya et de la dengue. 24 May 2011. [In French]. 15 April 2011. [Accessed 9 August July 2011]. Available at:

4. Institut de Veille Sanitaire. Points épidémiologique. Cir Sud. Province Alpes Côtes Azur et en Corse. 5 août 2011 .[In French]. [Accessed 9 August 2011]. Available at:


5. Gjenero-Margan  I, Aleraj B, Krajcar D et al. Autochthonous dengue fever in Croatia, August–September 2010. Eurosurveillance.  March 2011; 16.9 [Accessed 9 August 2011]. Available at:

6. Genchi C, Kramer LH, Rivasi F. Dirofilarial infection in Europe. Vector-Borne and Zoonotic Diseases. -Not available-, ahead of print. doi:10.1089/vbz.2010.0247.

7. Latvijas Infektologijas Centrs. Informacija Medijiem1.08.2011.Latvija pirmo reizi konstateta saslimšana ar filariozi [in Latvian]. [Accessed 9 August 2011]. Available at:

8. Hubalek Z, Halouzka J. West Nile Fever – a re-emerging Mosquito-borne viral disease in Europe. Emerg Inf Dis 1999:5:643-650.

9. Center for Disease Control and Prevention. Athens, Greece  West Nile [Accessed 8 August 2001]. Available at:


10. Hellenic Center for Disease Control and Prevention. KEELPNO. Weekly Epidemiological Report. West Nile Virus Infection Greece. 4 August, 2011. [Accessed 9 August 2011]. Available at:


11. European Centre for Disease Prevention and Control. West Nile Fever Maps. [Accessed 9 August 2011]. Available at:



12. The Ill Returned Traveller Ch. 4.2 In: Field VF, Ford L, Hill DR (Eds). Health Information for Overseas Travel. National Travel Health Network and Centre. London, UK. 2010.


ECDC Factsheet for Health Professionals: Chikungunya

ECDC website: West Nile virus

ECDC website: West Nile fever maps

NaTHNaC Health Information Sheet: Insect and tick bite avoidance

NaTHNaC Health Information Sheet: Dengue fever

NaTHNaC Health Information Sheet: West Nile virus

HPA website: West Nile virus

HPA website: Dengue fever

HPA website: Chikungunya fever