Health Professionals

Clinical Updates

1 August 2012

Risk of mosquito-borne disease: advice for travellers to the United States

Government health departments in the United States (US) provide advice for residents and visitors regarding the prevention of mosquito borne diseases that occur throughout the country [1-3]. 

There are several mosquito-borne diseases in the US, including West Nile Virus (WNV), Eastern equine encephalitis virus (EEEV) and dengue [4]. Since being introduced into the US in 1999, WNV has been reported from almost every continental state; in 2011 a total of 721 cases were reported from 43 states and the District of Columbia [5, 6]. As of 31 July 2012, 241 cases and four deaths have been reported in 2012 [6].

EEEV is a rare disease in humans. Most cases are reported from Florida, southeastern Georgia, southern Alabama, and the Carolinas [7].  In 2012, there has been one case reported in Florida [8].

The first cases of dengue occurred in Florida in 2009 after an absence of several decades. In 2010, 66 cases of locally acquired dengue were reported from Key West, Florida [9, 10]. No outbreaks of dengue have been reported in the US in 2011 and 2012 [11].

Advice for travellers

There is a very low risk of contracting these mosquito-transmitted viruses during travel to the US. The risk depends upon destination, season, length of exposure, and the intensity of disease transmission at time of travel. Certain groups are at increased risk; individuals over 50 years of age are at highest risk of developing severe WNV and those under 15 years and over 50 years are at increased risk of severe EEEV [4].

During travel to risk areas of the US, individuals should be aware of the risk and take appropriate mosquito bite avoidance measures. There are no vaccines that prevent WNV, EEEV or dengue.

Health professionals who see travellers with a characteristic febrile illness, who have returned from the US, should be alert to the possibility of mosquito borne disease. Relevant samples for testing together with a full clinical and travel history should be submitted to the Health Protection Agency Rare and Imported Pathogens Laboratory.

References

1. Centers for Disease Control and Prevention. West Nile Virus. Fight the bite. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm

2. Centers for Disease Control and Prevention.  Eastern Equine Encephalitis: Prevention. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/EasternEquineEncephalitis/gen/pre.html

3. Centers for Disease Control and Prevention. Dengue:Prevention. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/dengue/prevention/index.html

4. Centers for Disease Control and Prevention. National Centre for Infectious Diseases. Insect and Arthropod Diseases. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/ncidod/diseases/insects/diseases.htm

5. Centers for Disease Control and Prevention. West Nile Virus Disease and Other Arboviral Diseases — United States, 2011. MMWR. 61:510-514. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/mmwr/pdf/wk/mm6030.pdf

6. Centers for Disease Control and Prevention. West Nile Virus (WNV) activity reported to ArboNET, by state, United States, 2012 (as of July 31, 2012). [Accessed 1 August 2012]. Available at: http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCase

Count12_detailed.htm

7. Centers for Disease Control and Prevention. Eastern Equine Encephalitis: epidemiology and geographic distribution. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/easternequineencephalitis/tech/epi.html

8. Florida Department of Health. Mosquito-Borne Illness Advisory. 25 July 2012. [Accessed 1 August 2012]. Available at: http://www.doh.state.fl.us/environment/medicine/arboviral/

pdfs/2012/7-25-12WNV-Advisory-Duval.pdf

9. Florida Department of Health.Dengue Fever in Key West. [Accessed 1 August 2012]. Available at: http://www.myfloridaeh.com/medicine/arboviral/Dengue_

FloridaKeys.html

10. NaTHNaC Clinical Update. Locally acquired dengue: Key West, Monroe County, Florida, USA. 11 June 2010. [Accessed 1 August 2012]. Available at: http://www.nathnac.org/pro/clinical_updates/dengue_usa_

11. 11. Centers for Disease Control and Prevention. Dengue:Epidemiology. [Accessed 1 August 2012]. Available at: http://www.cdc.gov/Dengue/epidemiology/index.html

 

Links

Health Protection Agency: Rare and Imported Pathogens Laboratory

NaTHNaC Health Information Sheet: Insect bite avoidance