Keystone virus (''Keystone orthobunyavirus'') is a mosquito-borne

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

which can infect mammals. It was first discovered in animals in the

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

area, where it is spread in part by local species of ''

Aedes ''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', a particularly invasive spe ...

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

es. In 1964, a case of human infection, producing minor symptoms of a rash and fever, was circumstantially diagnosed. Conclusive laboratory demonstration of the virus in humans was first obtained and reported in 2018.Ashley May: "Keystone virus makes first jump from mosquitoes to humans with confirmed case in Florida teen, study says," https://www.usatoday.com/story/news/nation-now/2018/06/22/first-report-human-keystone-virus-found-florida-teen/725460002/, updated 1:20 p.m. ET June 25, 2018; "Authors said this was the first case of the virus in humans, but the Florida Department of Health told USA TODAY that a young child from Sarasota had the virus in 1964."

The virus

The Keystone virus was first discovered in mosquitoes in the Keystone area of

Tampa, Florida Tampa () is a city on the Gulf Coast of the United States, Gulf Coast of the U.S. state of Florida. The city's borders include the north shore of Tampa Bay and the east shore of Old Tampa Bay. Tampa is the largest city in the Tampa Bay area and ...

in 1964, based on

antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

ic evidence from specimens caught in 1963. The virus has been subsequently observed along the eastern and southern coastline of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, from Boston through Texas. In small mammals it can produce symptoms of

encephalitis Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations, ...

. Infection in humans is believed to be widespread, based on a 1972 report detecting Keystone virus

antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...

in 19–21 percent of the people tested in the Tampa Bay region. The first laboratory isolation of the virus from a human case occurred in Florida in 2016, and was reported in 2018. Identification took almost two years after the case actually occurred, when blood samples taken from the subject in 2016 were analyzed retrospectively by researchers studying the incidence of

Zika virus ''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active ''Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, whe ...

in the Florida population. The '' Aedes atlanticus'' mosquito is a demonstrated

vector Vector most often refers to: *Euclidean vector, a quantity with a magnitude and a direction *Vector (epidemiology), an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematic ...

. The virus transmits transstadially through the different stages of the insect's life: A female mosquito may lay eggs carrying the virus, which hatch into infected larvae, eventually maturing into adults that can infect mammals while injecting their

anti-coagulant Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where they ...

saliva during a bite.

References

Orthobunyaviruses Infraspecific virus taxa {{virus-stub