Orthohantavirus is a genus of viruses that includes all the types of hantavirus (family Hantaviridae) that cause disease in humans. Orthohantaviruses, hereinafter referred to as hantaviruses, are naturally found primarily in rodents. In general, each hantavirus is carried by one rodent species and each rodent that carries a hantavirus carries one hantavirus species. Hantaviruses in their natural reservoirs usually cause an asymptomatic, persistent infection. In humans, however, hantaviruses cause two diseases: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). HFRS is mainly caused by hantaviruses in Africa, Asia, and Europe, called Old World hantaviruses, and HPS is usually caused by hantaviruses in the Americas, called New World hantaviruses.
Hantaviruses are transmitted mainly through aerosols and droplets that contain rodent excretions, as well as through contaminated food, bites, and scratches. Environmental factors such as rainfall, temperature, and humidity influence transmission. HFRS is marked by kidney disease with kidney swelling, excess protein in urine, and blood in urine. The case fatality rate of HFRS varies from less than 1% to 15% depending on the virus. A mild form of HFRS often called nephropathia epidemica is often caused by Puumala virus and Dobrava-Belgrade virus. For HPS, initial symptoms are flu-like, with fever, headache, and muscle pain, followed by sudden respiratory failure. HPS has a higher case fatality rate than HFRS, at 30–60%. For both HFRS and HPS, illness is the result of increased vascular permeability, decreased platelet count, and overreaction of the immune system.
The hantavirus genome consists of three single-stranded negative-sense RNA segments that encode one protein each: an RNA-dependent RNA polymerase (RdRp), a spike glycoprotein precursor, and the N protein. Segments are encased in N proteins to form ribonucleoprotein (RNP) complexes that each have a copy of RdRp attached. RNP complexes are surrounded by a lipid envelope that has spike proteins emanating from its surface. Replication begins when spikes attach to the surface of cells. After entering the cell, the envelope fuses with endosomes and lysosomes, which empties RNPs into the cytoplasm. RdRp then transcribes the genome to produce messenger RNA (mRNA) for translation by host ribosomes to produce viral proteins and replicates the genome for progeny viruses. Old World hantaviruses assemble in the Golgi apparatus and obt
