Viruses and bacteria carried by mosquitoes and sometimes ticks are some of the most common causes of encephalitis throughout the world. Most people who are bitten by infected mosquitoes do not develop any symptoms or develop only a mild flu-like illness. For those who do develop encephalitis, symptoms may develop within a few days or up to 2 weeks after the mosquito bite occurred, depending on which virus the mosquito was carrying.
Encephalitis caused by mosquito-borne viruses is spread by the bite of an infected mosquito. It also may be transmitted through blood transfusions and breast-feeding. There is no proof that it can be passed from one person to another through casual contact or from an animal to a person.
The mosquito-borne viruses that cause encephalitis cannot be destroyed with antiviral or other medicines. Treatment for these types of encephalitis focuses on reducing symptoms and providing supportive care while the body heals.
If you have signs of encephalitis caused by bacteria, your doctor will prescribe antibiotics. This type of encephalitis is more common during tick season.
Types of encephalitis include:
Most cases of mosquito-borne encephalitis occur during the warmest months of the year, when mosquitoes are most active. In areas that are warm year-round, people may get encephalitis throughout the year.
Rocky Mountain spotted fever can cause encephalitis in some cases. It happens mostly in North, Central, and South America. In the United States, it is most common in the area between North Carolina and Oklahoma. This type of bacterial encephalitis is caused by a tick bite.
Other Works Consulted
- Jubelt B (2010). Viral infections and postviral syndromes. In LP Rowland, TA Pedley, eds., Merritt's Neurology, 12th ed., pp. 156–185. Philadelphia: Lippincott Williams and Wilkins.
- Ropper AH, Samuels MA (2009). Acute encephalitis section of Viral infections of the nervous system, chronic meningitis, and prion diseases. In Adams and Victor's Principles of Neurology, 9th ed., pp. 716–723. New York: McGraw-Hill.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||W. David Colby IV, MSc, MD, FRCPC - Infectious Disease|
|Last Revised||October 26, 2011|
Last Revised: October 26, 2011
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