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No. 5 – May 2018

Vectorborne Diseases

Vectorborne diseases account for more than 17% of all infectious diseases and kill about 700,000 people each year. Vectorborne infections can result in mild illness, including fever, muscle or joint pain, and rash, or more severe illness. Severe illness can include swelling of the brain, crippling pain, fetal abnormalities, or death. In fact, the English meaning of the name of one such disease, chikungunya, is “that which bends up,” a description of the contorted posture of people affected with that disease.

Vectorborne pathogens—bacteria, viruses, or parasites—are most commonly transmitted by mosquitoes or ticks. People and animals get infected through infective bites. For instance, malaria, is caused by a parasite transmitted by Anopheles mosquitoes, Zika by a virus transmitted by Aedes mosquitoes, and Lyme disease by bacteria transmitted by Ixodes ticks. Mosquitoes and ticks are the best known vectors. Others include flies, sandflies, fleas, triatomines (kissing bugs), and some freshwater snails.

Each year, mosquitoes—considered as the most dangerous animals in the world—are responsible for more human deaths than any other animal (50,000 times more deaths than are caused by sharks!). In 2016, the World Health Organization reported 216 million new cases of malaria and an estimated 445,000 deaths caused by malaria worldwide. Other pathogens spread by mosquitoes include dengue, yellow fever, West Nile, chikungunya, and Zika viruses.

Some vectorborne diseases have long been known; others have recently emerged because of globalization of travel and trade, human migration and activity, urbanization, and climate change. Three notable examples of vectorborne viruses that have been introduced to the Western Hemisphere in the past 20 years are West Nile (1999), chikungunya (2013), and Zika (2015–2016) viruses. Vectorborne diseases are especially difficult to predict, prevent, or control because vaccines are available for only a few such diseases and because mosquitoes and ticks are notoriously difficult to control and often can rapidly develop resistance to insecticides when control measures are used.

EID Articles about Vectorborne Diseases

Learn more about vectorborne diseases from these articles in the May issue of Emerging Infectious Diseases. For a quick overview, read the abstracts. Use the Advanced Article Search to find more articles.

• History of Mosquitoborne Diseases in the United States and Implications for New Pathogens reports that socioeconomics, not just climate, determine where these diseases become established.

• Spontaneous Abortion Associated with Zika Virus Infection and Persistent Viremia reports that the virus can persist in a woman’s blood up to 3 weeks after abortion.

• Multiple Introductions of Influenza A(H5N8) Virus into Poultry, Egypt, 2017 confirms that poultry are being infected by several sources, which indicates a serious threat for poultry and human health.

• Alkhurma Hemorrhagic Fever Virus RNA in Hyalomma rufipes Ticks Infesting Migratory Birds, Europe and Asia Minor indicates that migrating birds are carrying the virus farther than previously known.

• Fatal Visceral Leishmaniasis Caused by Leishmania infantum, Lebanon describes 5 child refugees from Syria who died because of late diagnoses and lack of awareness of this sandfly-transmitted disease.

• Borrelia miyamotoi senu lato in Père David Deer and Haemaphysalis longicornis Ticks adds to the list of organisms carried by this tick, which infests this endangered species of deer.

Sources and Additional Information

• Centers for Disease Control and Prevention. National Center for Emerging and Zoonotic Infectious Diseases, Division of Vector-Borne Diseases
• Centers for Disease Control and Prevention. Vital Signs: Illnesses on the Rise from Mosquito, Tick, and Flea Bites
• Centers for Disease Control and Prevention. Vital Signs: Trends in Reported Vectorborne Disease Cases—United States and Territories, 2004–2016
• Mace KE, Arguin PM, Tan KR. Malaria Surveillance — United States, 2015. MMWR Surveill Summ 2018;67(No. SS-7):1–28. DOI:
• U.S. President’s Malaria Initiative
• World Health Organization. Malaria
• World Health Organization. Vector-borne Diseases, Fact Sheet 2017

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Original Issue Publication Date: 05/30/2018
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