Andes virus

Andes virus (ANDV) is the most common cause of hantavirus pulmonary syndrome (HPS) in South America. It is transmitted mainly by the long-tailed pygmy rice rat. In its natural reservoir, ANDV causes a persistent asymptomatic or mild infection and is spread mainly through saliva. Humans usually become infected by inhaling aerosols of rodent saliva, urine, or feces. In humans, infection can lead to HPS, an illness characterized by an early phase of mild and moderate symptoms such as fever, headache, and fatigue, followed by sudden respiratory failure. The case fatality rate from infection is about 21–36%. Human-to-human transmission of ANDV is sometimes reported, but there is not a strong consensus on whether it can spread between people. Proposed ways of transmission between people involve close contact with an infected person.

The genome of ANDV is about 12.1 kilobases (kb) in length and segmented into three negative-sense, single-stranded RNA (–ssRNA) strands. The small segment encodes the viral nucleoprotein, the medium segment encodes two glycoproteins (Gn and Gc) that form the viral spike protein, which attaches to cell receptors for entry into cells, and the long segment encodes the viral RNA-dependent RNA polymerase (RdRp), which replicates and transcribes the genome. Genome segments are encased in nucleoproteins to form ribonucleoprotein (RNP) complexes that are surrounded by a viral envelope with spikes emanating from its surface.

ANDV replicates first by binding to receptors on the surface of cells. Virus particles, called virions, are then taken into the cell into endosomes, where a drop in pH causes the viral envelope to fuse with the endosome, which releases viral RNPs into the host cell. RdRp then transcribes mRNA, which is translated by ribosomes to make viral proteins, and produces copies of the genome for progeny viruses. New virions are assembled near the cell membrane, where virions bud from the cell membrane and use it to obtain their viral envelope and leave the cell. The virus's main way of evolution is by mutation, but recombination and reassortment of genome segments are possible.

Increased blooming and seeding of bamboos is implicated in elevated long-tailed pygmy rice rat populations and heightened ANDV frequency in rodents and humans. Apart from the long-tailed pygmy rice rat, Andes virus has also been found in various other Sigmodontinae rodent species in South America, most commonly the long-haired grass mouse. The virus was first identified in 1995 in Argentina and is named after the Andes mountains. Sporadic outbreaks have occurred since its discovery, including in Argentina in 1996, in Chile in 1997–1998, in Argentina in 2018–2019, and aboard the MV Hondius in 2026.