Maintenance and Transmission of Rift Valley Fever Virus and Other Emerging Infectious Diseases in East and Central Africa

STUDY BACKGROUND

The East and Central Africa (ECA) region represents a unique environment to investigate RVF virus maintenance and transmission as it has reported the largest number of RVF epidemics. Recent studies have identified hotspots characterized by continuous low levels of human and livestock virus infections during the inter-epidemic periods (IEPs).

Although sheep are at highest risk of severe disease, how virus-host interactions differ between animal species is an area for further research. Seroprevalence and incidence studies at the wildlife, livestock, human interface are also important in understanding the nature of cross-species transmission. Our study will investigate the public health threat posed by RVFV during IEPs by determining the burden of human and livestock diseases, and the degree of sustained viral transmission in animal species during cryptic cycles. This will be carried out through surveillance among humans, livestock and wildlife. Understanding virus maintenance especially within the environment, vectors and wildlife populations will aid in identifying potential risk factors for RVFV infection in order to prevent future outbreaks.

While disease occurrence among animals may frequently go unnoticed due to inadequate animal surveillance systems and low levels of animal abortion, human disease may be the first indication that RVF virus amplification is occurring at high levels in a particular region . Furthermore, understanding the social aspects of disease transmission through human studies exploring human behaviour and cultural practices that lead to direct exposure to infected animal blood, tissues, secretions and excretions could provide valuable information to disease spill over dynamics . Additional knowledge of how routes for human exposure e.g. through mosquito bites or contact with infected animal products affect the immune response and disease outcomes is required . This will enhance global efforts in preparing for, and preventing, the possible spread of RVF disease to new regions.

While RVF may be an under-diagnosed cause of febrile illness within the ECA region it is important to consider the occurrence of other unknown or undiagnosed infectious diseases. Serious clinical disease due to a variety of pathogens in humans or animals is most likely missed in settings where health care access is limited and diagnostics scarce. Notably, multiple studies from the region report low levels of hospital visits, particularly among marginalized communities, including those in remote rural arid lands that have few health facilities and poorly functioning transport infrastructure that discourages traveling long distances to access health care. Over a third of suspected infectious diseases among humans go undiagnosed even when considerable testing is carried out; thus, many retrospective studies of emerging pathogens uncover cases in the region that occurred long before the pathogen was identified and epidemics reported.