Human Togaviruses and their diseases

Alphaviruses

Encephalitic Viruses

Eastern Equine Encephalitis (EEEV)- Originally native to Japan, it was spread to North America in shipments of tires containing the viral vector Aedes Albopictus, an eastern Tiger mosquito. Symptoms appear 5 to 15 days after being bitten by an infected mosquito, include high fever, headache, stiff neck and myalgia. One in three infected individuals will come down with the serious disease, two in three will be able to fight off the viral infection. The disease is fatal in 30-50% of cases

Western Equine Encephalitis (WEEV)- Most common of the Equine Encephalitises in the Midwest and Western portions of the United States. Transmitted via mosquito vector. Cases have been reported in Western USA, West Central Canada, Mexico and South America. Symptoms similar to EEE.

Venezuelan Equine Encephalitis (VEEV)- Arboviral disease that represents a threat throughout most of the Americas, including the United States. This virus has caused repeated epidemics and equine epizootics since the 1920s, involving up to hundreds of thousand of equines and tens of thousands of people with severe morbidity and mortality. Symptoms similar to EEE.

Everglades virus (EVEV)- A variation of VEEV. Antigenic and animal virulence studies show distinct differences between the endemic Florida strain, which has never been seen to cause overt disease in equines or humans, and the more virulent epizootic strains of VEE found in Central and South America led to the classification of the Florida strain of VEE as a separate Group A arbovirus now known as Everglades virus.

Arthritic Viruses-

Chikungunya (CHIKV)- characterized by sudden onset, chills and fever, and intense arthritic pain. The illness usually lasts 3-7 days. The word "chikungunya" is Swahili for "that which bends up," in reference to the stooped posture of patients afflicted with the severe joint pain associated with this disease. Chikungunya virus has been isolated from humans and mosquitoes in eastern, southern, western, and central Africa and in southeastern Asia, where it has been responsible for illnesses in hundreds to thousands of individuals.

O'nyong-nyong (ONNV)- Transmitted by Anopheles funestus and An. gambiae mosquitos . Following an incubation period of three to twelve days, the patient experiences myalgia and severe arthritis. Patients recover after about two weeks. 'O'nyong nyong' means 'weakening of the joints' in the Acholi dialect. The virus was first isolated during an epidemic in Acholi, Uganda. Several million subsequent cases were reported in Uganda, Kenya, Tanzania, Malawi and Mozambique during 1959 to 1961.

Ross River (RRV)- Causes the disease commonly know as epidemic polyarthritis (EPA), was first isolated in 1963. The disease is most common in eastern Australia though it has been diagnosed throughout Australia. Ross River Virus is characterised by arthritic symptoms.

Barmah Forrest (BFV)- Generally characterised by arthritic symptoms, similar to that of Ross River virus. Cases of Barmah Forest virus have been diagnosed throughout eastern Australia, especially in the northern state of Queensland.

Mucambo virus (MUCV)-

Sindbis (SINV)- Characterized by coincident onset of fever with rash and arthritic pain. Sindbis is found in Africa, India, and Malasia, and has been observed to reach epidemic proportions in Egypt and South Africa.

Mayaro- Also characterized by rash, fever, and arthritic pain, Mayaro is found in Central and South America. Many epidemics have been reported in the Amazon Basin.

Semliki Forest Virus (SFV)-

Rubiviruses

Rubella (RUBV)- A highly contagious mild infection of early childhood. Often refered to as the "German Measles", due to the diffuse maculopapular rash and fever it causes. When infection occurs during pregnancy, especially during the first trimester the virus is extermely teratogenic. Fetal infection is likely and often causes congenital rubella syndrome (CRS) resulting in abortions, miscarriages, stillbirths, and severe birth defects. Up to 20% of the infants born to mothers infected during the first half of pregnancy have CRS. The most common congenital defects are cataracts, heart disease, sensorineural deafness, and mental retardation.