Filoviruses

Filoviruses are a group of enveloped, filamentous viruses in the family Filoviridae. They are negative-sense single-stranded RNA viruses that cause severe viral hemorrhagic fevers in humans and nonhuman primates. The two main genera are Ebolavirus and Marburgvirus; notable species include Zaire ebolavirus, Sudan ebolavirus, Tai Forest virus, and Marburg marburgvirus. Outbreaks can have high case-fatality rates and require rapid public health responses.

Filoviruses have nonsegmented, negative-sense RNA genomes of about 19 kilobases that encode seven structural proteins: nucleoprotein (NP), viral protein 35 (VP35), VP40, glycoprotein (GP), VP30, VP24, and the large RNA-dependent RNA polymerase (L). Virions are filamentous, pleomorphic enveloped particles that can appear as straight filaments or curled shapes. The viruses replicate in the cytoplasm of infected cells and assemble and bud at the plasma membrane.

Natural reservoirs are thought to be fruit bats, with human infections typically resulting from contact with infected animals or bodily fluids; human-to-human transmission occurs through contact with blood, secretions, or contaminated materials and is most efficient in healthcare or caregiving settings. Outbreaks have occurred primarily in Africa, with notable events including Marburg outbreaks and Ebola outbreaks in West and Central Africa; outbreak size and case fatality rate vary by virus species and setting.

Clinical features range from abrupt onset fever, fatigue, myalgia, and headache to gastrointestinal symptoms, hemorrhagic manifestations, and multi-organ failure in severe cases. Diagnosis relies on molecular tests (RT-PCR) or antigen detection; samples require high biosafety levels. No specific antiviral treatment is widely available, but supportive care improves outcomes. Two FDA-licensed monoclonal antibody therapies (Inmazeb and Ebanga) target Zaire ebolavirus, and the rVSV-ZEBOV vaccine (Ervebo) is used to prevent Ebola virus disease in at-risk populations.

Public health measures, including rapid diagnosis, isolation, contact tracing, infection control, and ring vaccination during outbreaks, remain central to controlling filovirus disease.