Bas-Congo virus

The Bas-Congo virus (BASV), named after the DRC's area of Bas-Congo, in which it was first discovered, is a novel rhabdovirus associated with a small outbreak of hemorrhagic fever in Mangala village in 2009.^[1] The disease is characterized by a fulminant course and can be fatal. In the 2009 outbreak, two out of three people died. The surviving patient and a further asymptomatic person developed antibodies against BASV.

Discovery

The virus was discovered after the exclusion of all known viral agents causing hemorrhagic fever. RNA copies of BASV were found in the serum of the patient who survived the disease. The genome was assembled using the deep sequencing method. Phylogenetic analysis revealed rather big differences to other known rhabdoviruses. Two people, a surviving nurse and a close contact, developed antibodies highly specific for the BASV glycoprotein (BASV-G). Neutralization was observed only with BASV-G and not with pseudoviruses carrying the glycoprotein of the related rhabdovirus vesicular stomatitis virus (VSV-G) thus indicating that BASV was the actual cause of the outbreak.

A rhabdovirus causing hemorrhagic fever in humans seems strange at first glance for no member of this family has been associated with this kind of disease in humans before. However, fish can suffer from viral hemorrhagic septicemia, a disease caused by a member of the novirhabdovirus genus that leads to bleedings. Most relevant to humans are the different species of the genus lyssavirus causing rabies.

Symptoms and transmission

The disease associated with Bas-Congo virus is a severe acute hemorrhagic fever characterized by rapid disease progression. However, there are clues to asymptomatic infections as well. The onset is sudden, symptoms include high fever, malaise, nausea, vomiting, diarrhea, abdominal pain, headache and fatigue. Bleedings appear very early in the course of the disease, including nose bleeding, mouth bleeding and hematemesis. In the 2009 outbreak, death occurred two or three days after the onset of symptoms.

The first patient in Malaga village was a 15-year-old boy attending the local school. He died two days after he became ill. A 13-year-old girl attending the same school developed symptoms a few days later and died three days thereafter. The two students were in different classes and had no evident personal contact in the weeks before the outbreak. The source of primary infection remains unknown. A male nurse working in the local health center visited by the first victims showed signs of the disease 9 days after the girl's death. This indicates human-to-human transmission of BASV through body fluids and close contact; transmission through aerosol would most likely result in more cases.

A fourth person directly caring for the nurse developed antibodies against BASV but remained asymptomatic.

References