"Vectors" are microorganisms (i.e., parasite, virus, bacteria) that transmit disease from human and animal host sources to other humans – this typically happens when the organism obtains a blood meal from an infected host (human or animal) and later transmits it into a new host during another blood meal.
Most vectors are insects (i.e., mosquitoes, ticks, flies, fleas or lice), so some common diseases are referred to as insect-borne diseases. However, the broader name of these diseases is
vector-borne diseases or VBD.
NOTE: Not all VBD are specifically monitored by military diseases experts – those listed on this page are required to be reported by military treatment facilities as a Reportable Medical Event (RME). Specification of the disease type (or if neuroinvasive or non-neuroinvasive) is also required. See DHA guidance for military healthcare providers: Communicable Disease Toolkit (CDT).
Some VBD are associated with insects found in the U.S. (e.g., Lyme disease caused by the lone star tick). Others are associated with areas outside the continental U.S. especially with poor sanitation quality and tropical climates – these include malaria, dengue, and Zika. Traveling and deployment to these areas increases risk.
Though recent health surveillance data
indicates Lyme disease, Rocky Mountain Spotted Fever (RMSF), Malaria, and Dengue are the 4 most diagnosed VBDs in the military population, the medical clinics where cases are diagnosed may not be the same the locations where personnel are originally bitten by vector.
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Types of VBD
VBD can be sub-grouped into the following 3 categories:
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Arboviral Diseases. A sub-category of over 130 VBD diseases caused by arthropod-borne viruses ('arboviruses') transmitted to humans primarily through the bites of infected mosquitoes, ticks, sand flies, or midges. Some may also be transmitted through mother-to-fetus, breast milk, blood transfusion, organ transplant, or laboratory exposures. Arboviral diseases are typically grouped into two primary categories based on clinical effects:
· Neuroinvasive diseases (e.g., Japanese encephalitis virus (JEV) which results in severe encephalitis (brain inflammation) or paralysis)
· Non-neuroinvasive diseases (e.g.,
Chikungunya, Dengue, West Nile Virus,
Yellow Fever, Zika) These diseases are the most common form of arboviral diseases and are associated with acute fever with other possible symptoms such as aches and pains (headaches or eye pain behind the eyes, muscle, joint, or bone pain), nausea/vomiting, and/or rash. Rest, fluids, and pain medications may relieve symptoms, but there are no disease-specific treatments.
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Mosquito-borne (e.g., parasites causing malaria and some arboviral diseases)
More info:
· Malaria Among Members of the U.S. Armed Forces, 2023
· Military veterans information on malaria
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Tick-borne (e.g., Lyme, Babesiosis)
See articles:
· A Review of Force Health Protection Aspects of Lyme Disease in the U.S. Military (2025)
· Lyme disease continuing to crawl - Protect yourself (2022)
· Communicable Disease Toolkit (CDT) – military diagnostic criteria for required reporting
Other:
***NEWS May 2025*** Screw Worms – increasing rates
While
largely a vector-borne disease that affects livestock, the larvae (maggots) of the New World Screwworm (NWS) Fly burrow into the tissue and feed on the living flesh of warm-blooded animals (most commonly livestock farm animals) and occasionally humans. NWS is endemic in South America, parts of Central America, and some Caribbean islands; the cases of disease have increased and are occurring in other areas such as Mexico (as of May 2025).
NWS female flies deposit eggs on or near pre-existing wounds or on mucous membranes inside the nose, mouth, and ears. Eggs hatch into larvae in approximately 7 days, after which they drop from the host and pupate emerges from the soil after 7 to 54 days depending on temperature and humidity. Human cases can occur among people who tend livestock in endemic areas, and in travelers to these regions, particularly among people with open wounds who sleep outdoors. Untreated infestations can result in severe tissue destruction and are potentially fatal.
Reducing Risk of VBD
Service members should
learn the VBD threats in local areas and especially prior to travelling or deploying and follow these two primary DoD VBD prevention tactics to reduce risk of a VBD:
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Comply with the
DoD’s Insect Repellant System, which includes wearing insect repellent on exposed skin and wearing uniforms treated with permethrin, an insecticide. Since several types of vectors can bite both indoors and outdoors all day, it is important to ensure protection throughout the entire day. For example, service members deployed or stationed where there is threat of mosquito-borne diseases must protect themselves and their families by wearing permethrin-treated uniforms/clothing, using insect repellents containing DEET, picaridin and IR3535 (all of which are recognized by CDC as safe for pregnant women when used as directed on the product label). See Personal Protection Measures outlined in
Technical Guide No. 36.
Knowing when and where the insect vector(s) feed can also help avoid exposure to vectors of concern. For example, mosquitoes are attracted to stagnant water supplies (avoid, remove, or cover contained water), and ticks are more prone to grassy woody areas. Learn about vector threat habitats and times of day in areas that you will be in.
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Properly take any vaccines or preventive medications (prophylaxis), including completing any prophylaxis medications after return.
DoD specifies requirements for vaccines and prophylaxis medications based on worldwide regions of deployment. Civilians can proactively investigate what prophylaxis or vaccines are recommended for an area of travel by using the
CDC Travelers' Health guide.
It is critically important to obtain medication from your provider prior to travel and to take it as prescribed. If during or after return you experience illness such as a high or recurrent fever, seek medical care immediately, and inform your provider about your recent travel risk.
NOTE:As of 7/2024, the military only uses VBD vaccines for tick-borne encephalitis, Japanese encephalitis, and yellow fever for service members stationed or deployed to endemic areas. Other VBD vaccines may only be approved for children, such as malaria and dengue, or are still so new that policies on their use have not been incorporated into military requirements (such as for chikungunya). Instead of vaccines for most VBDs the military opts for prophylaxis medications (such as for malaria), or post-exposure treatment using an antibiotic (such as doxycycline for tick-borne illnesses like Lyme) – both which are effective and used by civilians.
Additional Resources
VBD threats by world areas and recommended prophylactic medicines/vaccines:
Preventing exposure (prevent bug bites):
