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This week begins a new series on the hemorrhagic fevers. These are typically viral infections that can frequently present with symptoms of bleeding and high fever. However, bleeding is not particularly sensitive or specific for many of the hemorrhagic fevers. Indeed, many of these infections initially present with much more generic, flu-like symptoms. Nevertheless, many of these infections do share two very important features. First, many (but, not all) of the viruses causing hemorrhagic fever are zoonotic in origin, which can create difficulty in identifying the sources of outbreaks, as well as implementing effective control measures. Second, many of these infections are highly virulent and potentially associated with high mortality in outbreak settings. Two of the hemorrhagic fevers have already been covered at Infection Landscapes, namely dengue fever and yellow fever.
Viral hemorrhagic fevers are caused by RNA viruses in the following four families:
Flaviviridae: These are enveloped viruses with single-stranded RNA genomes. Those that cause hemorrhagic fever are generally arthropod-borne, and include dengue virus and yellow fever virus.
We have already covered the major hemorrhagic fevers in the Flaviridae family, so these will not be revisited in this series. However, we will cover all the major viruses that cause hemorrhagic fevers in the remaining three families. Next time, we will begin with the Bunyaviridae family, and with the hantaviruses in particular.
This week begins a new series on the hemorrhagic fevers. These are typically viral infections that can frequently present with symptoms of bleeding and high fever. However, bleeding is not particularly sensitive or specific for many of the hemorrhagic fevers. Indeed, many of these infections initially present with much more generic, flu-like symptoms. Nevertheless, many of these infections do share two very important features. First, many (but, not all) of the viruses causing hemorrhagic fever are zoonotic in origin, which can create difficulty in identifying the sources of outbreaks, as well as implementing effective control measures. Second, many of these infections are highly virulent and potentially associated with high mortality in outbreak settings. Two of the hemorrhagic fevers have already been covered at Infection Landscapes, namely dengue fever and yellow fever.
Viral hemorrhagic fevers are caused by RNA viruses in the following four families:
Flaviviridae: These are enveloped viruses with single-stranded RNA genomes. Those that cause hemorrhagic fever are generally arthropod-borne, and include dengue virus and yellow fever virus.
Dengue virus (cluster of black spots)
Bunyaviridae: These are enveloped viruses with single-stranded RNA genomes in three segments. Most of those that cause hemorrhagic fever are arthropod-borne, except the Hantaviruses, which are rodent-borne. These viruses include the Hantaviruses, Nairoviruses, and Phleboviruses.
Hantavirus
Filoviridae: These are enveloped viruses with single-stranded RNA genomes, further characterized by a distinctive, pleomorphic thread-like structure that can take on circular, branched, or coiled shapes. These viruses cause severe infections in humans, while the natural reservoir is probably fruit bats. These viruses are transmitted zoonotically and nosocomially.
Ebolavirus
Arenaviridae: These are enveloped viruses with single-stranded RNA genomes in two segments. Those that cause hemorrhagic fevers are generally rodent-borne, and include Lassa virus, Machupo virus, Junin virus, Sabia virus, and Guanarito virus.
Lassa virus
We have already covered the major hemorrhagic fevers in the Flaviridae family, so these will not be revisited in this series. However, we will cover all the major viruses that cause hemorrhagic fevers in the remaining three families. Next time, we will begin with the Bunyaviridae family, and with the hantaviruses in particular.