Abstract:
The genus Alphavirus in the family Togaviridae consists of approximately 30 single
stranded, positive-sense RNA viruses which cause diseases ranging from mild, febrile
illness with rash and arthritis to life-threatening encephalitis. Sindbis virus is the prototype virus for this genus and is the most widely distributed alphavirus globally.
Little epidemiological data exists for this virus due to inadequate surveillance efforts
in most countries, and it is suspected that Sindbis and other alphavirus infections are
largely underreported. Additionally, changing patterns of alphavirus infections are
challenging conventional knowledge of these diseases and have created the need for
improved diagnostic methods and increased vigilance and disease surveillance around
the globe.
To date, no real-time PCR assay exists that is able to detect all of the medically
important (and other) alphaviruses. This study was therefore aimed at developing and
evaluating such an assay in order to improve the diagnostic and surveillance activities
of these viruses in South Africa. Additionally, this study was aimed at providing
novel information on the molecular and epidemiological characteristics of Sindbis
virus in South Africa, and to provide insights in the diversity of this virus compared to
elsewhere in the world.
This study has revealed that an outbreak of Sindbis fever occurred during 2010, with
the Free State and Northern Cape Provinces being most affected. The outbreak
coincided with an outbreak of Rift Valley fever. The risk for acquiring a Sindbis
virus infection was found to be highest during late summer/early autumn, and was
slightly higher among males of increasing age. The phylogenetic results obtained in
this study have demonstrated that Sindbis isolates form five separate groups with a
considerable amount of genetic variation among these groups. The grouping of the
isolates corresponded to the major migratory patterns of birds, suggesting that birds
may play a large role in the dispersal of Sindbis viruses between continents. In
addition, a real-time reverse transcription PCR assay has been developed which is
able to detect Sindbis virus and other medically important alphaviruses with varying
sensitivities. This project contributes to the update of epidemiological and
phylogenetic data on Sindbis virus in South Africa and delivers potential tools for
improved surveillance activities of alphaviruses in future.
