Family: Phenuiviridae
Genus: Tanzavirus
Distinguishing features
Dar es Salaam virus (DeSV) is assigned to Tanzavirus daressalaamense the only species in the genus. Tanzavirus RNA was found in a human plasma sample from Tanzania in 2014. The tanzavirus genome has three genes, encoding a large protein (L), the external glycoproteins (Gn and Gc) and a nucleocapsid protein (N). Based on well-supported Maximum Likelihood or Maximum Clade Credibility trees inferred from complete L protein sequences, viruses classified in the genus Tanzavirus form a monophyletic cluster clearly distinguished from other phenuivirids. There currently is no cultured tanzavirus isolate (Laubscher et al., 2019).
Virion
Morphology
Virion morphology is unknown. Based on the putative proteins encoded by the virus genome, the virion is probably a filamentous virion without an envelope.
Nucleic acid and Protein
The tanzavirus genome encompasses three segments of negative-sense RNA; L (6.5 kb), M (3.8 kb), and S (1.3 kb). Analysis of the terminal sequences has yet to be completed. All three genomic RNAs contain untranslated regions flanking a single ORF which, based on comparisons with other negative-sense RNA viruses, is predicted to be contained in the virus complementary strand. The L segment (6.5 kb) encodes a protein with a predicted molecular mass of 248 kDa that is homologous with the bunyaviral RNA-directed RNA polymerase (RdRP) domain. The M segment (3.8 kb) encodes a protein of 131 kDa that is homologous with the phlebovirus glycoprotein G1 and G2 sequences, and with the phlebovirus glycoprotein C-terminal Ig-like domain. The S segment (1.3 kb) encodes a protein of 28 kDa that is homologous with the tenuivirus/phlebovirus N domain (Table 3.Phenuiviridae) (Laubscher et al., 2019).
Genome organization and replication
Tanzavirus genome arrangement is similar to that of beidiviruses, citriciviruses, goukoviruses, hudiviruses, hudoviruses, phasiviruses and pidchoviruses (Figure 1.Tanzavirus). The three segments putatively encode L, a glycoprotein precursor (comprising Gn and Gc), and N, respectively. The Gn and Gc glycoproteins of 76 kDa and 54 kDa were earlier referred to as G1 and G2 based on apparent size following gel electrophoresis. The tanzavirus genome does not encode the non-structural proteins NSm or NSs. Details of virus replication are unknown (Laubscher et al., 2019).
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| Figure 1.Tanzavirus. Genome organization of a tanzavirus. Coloured boxes depict ORFs that encode N, nucleocapsid protein; Gn and Gc, external glycoproteins; and L, large protein. |
Biology
Tanzavirus RNA was found by high-throughput sequencing of plasma from an HIV-negative 43-year-old male with a 3-day history of fever, headache and back pain, and 2 days of pollakiuria. Whether or not tanzavirus has a wider host range is unknown (Laubscher et al., 2019).
Species demarcation criteria
Not defined as the genus currently includes only a single species.