Biomedical Engineering Reference
In-Depth Information
*Getah virus
*Mayaro virus
*Mucambo virus
*O'nyong'nyong virus
*Ross river virus
*Barmah forest virus
*Sagiyama virus
*Semliki forest virus
*Sindbis virus
*Tonate virus
*Venezuelan equine encephalomyelitis virus
*Western equine encephalomyelitis virus
Rubivirus
*Rubella virus
Class Togaviridae is named for its distinctive coat (the “toga”). Togaviruses have
a genome approximately 12 000 kilobases in length, somewhat larger than the
genome of Class Picornaviridae. Togaviruses live in the cytoplasm of their host
cells, where viral replication and gene expression take place. Class Togaviridae
contains two subclasses: Class Alphavirus and Class Rubivirus. All the members
of Class Alphavirus are arboviruses (arthropod-borne viruses) spread by mosqui-
toes (primarily) or ticks. Class Rubivirus contains only one species that is infec-
tive in humans: Rubella virus, the cause of German measles. Rubella is spread
directly from person to person, without an insect vector. Readers should not con-
fuse Rubella virus with the measles virus, Rubeola. Rubeola virus is a paramyxo-
virus (Group V, Chapter 43), unrelated to Rubella virus.
A few of the alphaviruses typify the group. Chikungunya is a disease that
produces a clinical syndrome similar to that seen with Dengue virus (Class
Flaviviridae), Ross river virus and Barmah forest virus; namely, an acute febrile
phase followed by a prolonged arthralgic phase. Chikungunya fever is spread by
the Aedes mosquito, and the reservoir is primarily human (i.e. transmission is
human to mosquito to human). In recent years, the incidence of Chikungunya
has recently increased in Asia and Africa and is now an emerging disease in
Europe [76].
Ross river virus and Barmah forest virus produce clinically and geographic-
ally indistinguishable diseases, sometimes referred to collectively as epidemic
polyarthritis. The diseases are spread by various species of mosquito, and
both are endemic to Australasia. They produce an acute influenza-like illness,
followed by arthralgia. Joint pains may persist for many months. The reservoir
for both viruses seem to be, primarily, marsupials.
Group IV (
)ssRNA
Flaviviridae
Hepacivirus
*Hepatitis C
1
