When it comes to hemorrhagic fevers, Ebola and Marburg tend to
get the lions’ share of the press. Both are highly fatal, both
can cause people to die in excruciating ways, and both have come
to represent somewhat our fear of and fascination with emerging
exotic diseases. However, as I’ve pointed out previously, as far
as actual fatalities–or even illnesses go–both viruses are small
potatoes. Other viruses that can also have hemorrhagic
manifestations–including dengue and yellow fever–are much more
common. One of these other viruses that frequently causes
hemorrhagic fever is Rift Valley fever (RVF), an arbovirus
(arthropod-borne) found primarily in Africa.  The RVF virus can
be spread by mosquitoes, and more commonly infects domestic
animals (such as cattle and sheep) than it does humans. Indeed,
a clue that an outbreak of RVF is in progress in animals is the
sudden onset of spontaneous abortions in livestock: the abortion
rate among infected, pregnant ewes is close to 100% for this
virus, for example. Additi