Chikungunya in the context of Aedes albopictus

Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people contract mosquito-borne illnesses each year, resulting in nearly a million deaths.

Diseases transmitted by mosquitoes include malaria, dengue, West Nile virus, chikungunya, yellow fever, filariasis, tularemia, dirofilariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, Eastern equine encephalitis, Venezuelan equine encephalitis, Ross River fever, Barmah Forest fever, La Crosse encephalitis, and Zika fever, as well as newly detected Keystone virus and Rift Valley fever. A preprint by Australian research group argues that Mycobacterium ulcerans, the causative pathogen of Buruli ulcer is also transmitted by mosquitoes.

Aedes aegypti (/ˈiːdiːz eɪˈdʒɪpti/; US: /eɪdz -, ˈeɪdiːz -/; from Ancient Greek αηδής (aēdḗs) 'unpleasant' and Latin aegyptī 'Egyptian') – sometimes called the Egyptian mosquito, dengue mosquito, or yellow fever mosquito – is a mosquito that spreads diseases such as dengue fever, yellow fever, and chikungunya. The mosquito can be recognized by black and white markings on its legs and a marking in the form of a lyre on the upper surface of its thorax. The mosquito is native to north Africa, but is now a common invasive species that has spread to tropical, subtropical, and temperate regions throughout the world.

Dengue virus (DENV) is the cause of dengue fever. It is a mosquito-borne, single positive-stranded RNA virus of the family Flaviviridae; genus Orthoflavivirus. Four serotypes of the virus have been found, and a reported fifth has yet to be confirmed, all of which can cause the full spectrum of disease. Nevertheless, the mainstream scientific community's understanding of dengue virus may be simplistic as, rather than distinct antigenic groups, a continuum appears to exist. This same study identified 47 strains of dengue virus. Additionally, coinfection with and lack of rapid tests for Zika virus and chikungunya complicate matters in real-world infections.

Dengue virus has increased dramatically within the last 20 years, becoming one of the worst mosquito-borne human pathogens that tropical countries have to deal with. Estimates published in 2013 indicate that as many as 390 million infections occur each year, and many dengue infections are increasingly understood to be asymptomatic or subclinical.

A maculopapular rash is a type of rash characterized by a flat, red area on the skin that is covered with small confluent bumps. It may only appear red in lighter-skinned people. The term "maculopapular" is a compound: macules are small, flat discolored spots on the surface of the skin; and papules are small, raised bumps. It is also described as erythematous, or red.

This type of rash is common in several diseases and medical conditions, including scarlet fever, measles, Ebola virus disease, rubella, HIV, secondary syphilis (congenital syphilis, which is asymptomatic, the newborn may present this type of rash), erythrovirus (parvovirus B19), chikungunya (alphavirus), Zika fever, smallpox (which has been eradicated), varicella (when vaccinated persons exhibit symptoms from the modified form), heat rash, and sometimes dengue fever. It is also a common manifestation of a skin reaction to the antibiotic amoxicillin or chemotherapy drugs. Cutaneous infiltration of leukemic cells may also have this appearance. Maculopapular rash is seen in graft-versus-host disease (GVHD) developed after a hematopoietic stem cell transplant (bone marrow transplant), which can be seen within one week or several weeks after the transplant. In the case of GVHD, the maculopapular lesions may progress to a condition similar to toxic epidermal necrolysis. In addition, this is the type of rash that some patients presenting with Ebola virus hemorrhagic (EBO-Z) fever will reveal but can be hard to see on dark skin people. It is also seen in patients with Marburg hemorrhagic fever, a filovirus not unlike Ebola.