What Are Arenaviruses (Arenaviridae)?

Arenaviruses, classified under the Arenaviridae family, are enveloped, single-stranded RNA viruses that cause various diseases in both humans and animals. These viruses derive their name from Latin, referring to their distinctive appearance of small, sand-like particles when observed under an electron microscope.

Virions of arenaviruses are roughly spherical and have a diameter ranging from 50 to 300 nanometers (nm). They possess an outer envelope that is composed of a lipid bilayer derived from the host cell's plasma membrane during budding. The envelope also contains glycoproteins responsible for attachment to and entry into host cells.

Inside the virion, the arenaviral genome consists of two linear, single-stranded RNA segments designated as the large (L) segment and the small (S) segment. These segments encode for proteins essential for viral replication, assembly, and pathogenesis.

The L segment carries the genetic information for the viral RNA-dependent RNA polymerase (RdRp), which is crucial for viral transcription and replication of both L and S segments. Additionally, the L segment encodes for a nucleoprotein (N) and a glycoprotein precursor (GPC) that is further processed into two subunits, GP1 and GP2.

The S segment encodes the viral matrix protein (Z) and the nucleoprotein (NP), which associates with viral RNA to form the nucleocapsid. The NP plays a critical role in initiating and regulating genome replication.

Arenaviruses are divided into two main groups: Old World arenaviruses and New World arenaviruses. Old World arenaviruses, found in Africa, Asia, and Europe, include viruses like Lassa virus, which causes Lassa fever, and lymphocytic choriomeningitis virus (LCMV), a non-pathogenic virus in humans but an important model for studying immunology and virology.

New World arenaviruses are found in the Americas and include viruses like Junín virus, the causative agent of Argentine hemorrhagic fever, and Machupo virus, responsible for Bolivian hemorrhagic fever.

Arenaviral infections can manifest in a range of clinical presentations, from mild febrile illnesses to severe hemorrhagic fevers. Symptoms may include fever, muscle aches, headache, nausea, vomiting, and bleeding disorders. The severity of the disease and the risk of hemorrhagic complications vary depending on the specific virus.

Arenaviruses can be transmitted through contact with infected animals or through direct contact with infected individuals' bodily fluids or contaminated materials. Some arenaviruses, like Lassa virus, are known to be transmitted via aerosolization.

Prevention and control measures for arenaviral infections include practicing good hygiene, avoiding contact with infected individuals, and implementing vector control strategies. Vaccination is available for some arenaviruses, such as the LCMV vaccine used in research settings and the Junín virus vaccine used in Argentina.

Due to their potential to cause severe disease and outbreaks, arenaviruses are classified as Biosafety Level 3 (BSL-3) or BSL-4 pathogens, requiring special handling and containment facilities for laboratory work.

In summary, arenaviruses are single-stranded RNA viruses that belong to the Arenaviridae family. They can cause a spectrum of diseases, from mild febrile illnesses to severe hemorrhagic fevers. Understanding their transmission, pathogenesis, and developing effective prevention, and treatment strategies are crucial for managing arenaviral infections and mitigating their impact on public health.