Via The Lancet Global Health: Rift Valley fever: still an emerging infection after 3500 years. Excerpt:
In the Book of Exodus, the description of the fifth plague of Egypt evokes a high mortality epizootic disease affecting livestock such as camels, goats, and sheep. It is debatable whether Rift Valley fever was that biblical plague but it is undeniably an ancient zoonosis and its modern history is no less dramatic.
The virus was first isolated in 1930 after a heavy mortality of newborn lambs was reported on a Merino sheep farm in Naivasha, Rift Valley, Kenya following unusually heavy rainfall. The associated human disease was identified 20 years later in South Africa and the relevant microbiology, clinical disease, ecology, and epidemiology seemed to be well established. This dominant disease narrative continues to be punctuated by multiple novel revelations including those reported in The Lancet Global Health by Maria Baudin and colleagues.
Rift Valley fever is mainly a disease of animals with enzootic and epizoonotic mosquito-borne transmission cycles associated with corresponding endemic and epidemic disease in human beings based on a complex set of relationships between domesticated animals, the vectors, human behaviours, local ecology, and climate.
The disease has long been characterised by waves of spontaneous abortions among domesticated animals and severe illness of pregnant animals and newborns that often heralds human infections. Human infections are generally subclinical or self-limited although it can be associated with a severe febrile illness and jaundice. Less than 5% develop the three major complications: encephalitis, retinitis and other ocular lesions, and a haemorrhagic fever.
Transmission to human beings is mainly from direct or indirect contact with infected animals and their organs but disease has also been transmitted by mosquitoes and by aerosols generated in the laboratory. Vaccines are available for animals to limit the substantial economic impact of the disease.
Rift Valley fever was considered to be limited to sub-Saharan Africa until it caused an epidemic in Egypt in 1977. It was then considered confined to Africa until an outbreak in Saudi Arabia and Yemen in 2000. Now it is recognised as an agricultural threat to the rest of the Middle East and other countries with competent mosquito vectors.
Similarly, the disease has never been associated with person-to-person transmission including the reassuring lack of nosocomial infections even among health-care workers tending to patients with haemorrhagic fever. This dogma was altered in this century by two case reports of vertical transmission.
Baudin and colleagues extend these case reports with a large study that presents the unique observation of spontaneous abortions among febrile patients in Port Sudan infected with Rift Valley fever.