Keeping up with Virus Taxonomy: seasonal viruses

Posted on January 23, 2025   by Clare Baker

Welcome back to ‘Keeping up with Virus Taxonomy’ and the first edition of 2025! For this edition, we’ll be taking a look at families of viruses that make you say ‘there’s something going round at the moment’ — seasonal viruses. 

Caliciviridae 

Let’s start off with a family of viruses that include noroviruses, the leading cause of acute gastroenteritis in humans — Caliciviridae. Transmission of caliciviruses can be via direct contact with an infected host or indirectly via contact with faecal material; vomit or respiratory secretions; contaminated food; water or fomites (objects or materials that carry infection). But it’s not just humans who are at risk from transmission of caliciviruses, the family includes seven genera which infect mammals, two which infect birds and two which infect fish. Unclassified caliciviruses have also been detected in geese, yellowfin seabream, greater green snake, arctic lamprey, frogs and various Australian birds. 

Pneumoviridae 

Keeping to the theme of seasonal viruses, our next family of viruses contains viruses that are specific and pathogenic for humans: human respiratory syncytial virus and human metapneumovirus (HMPV). Human pneumovirus infection takes place in the respiratory tract, causing respiratory tract disease. In general, pneumovirus infections are limited, and eliminated by host immunity. Transmission between host species also may occur in some cases for HRSV and HMPV in humans and chimpanzees.  

Let’s take a closer look human syncytial virus, strain A2 (HRSV-A2). Virions of this virus consist of spherical and filamentous forms and can have considerable variation in size and shape. Multiploid  virions (with multiple sets of chromosomes) have been found but the vast majority of virions contain a single functional genome.  

Paramyxoviridae 

Talking of throat infections, you may have come across a seasonal throat infection in children called croup. Croup is often caused by the parainfluenza virusi, which belongs to the Paramyxoviridae family. The family consists of large enveloped RNA viruses which infect mammals, birds and in some cases, reptiles and fish. Measles, mumps, Nipah and Hendra viruses also belong to this family and most viruses have a narrow host range in nature but can infect a broader range of cultured cells. Virus transmission is horizontal, mainly through direct contact and airborne routes.  

Picornaviridae  

The Picornaviridae family is a family of small icosahedral viruses with single-stranded, highly diverse positive-sense RNA genomes. The family contains a group of viruses called enteroviruses which are often referred to as “the summer flu” as they spread during the summer and autumnii.  While picornaviruses can cause mild symptoms like a common cold or subclinical infections in animals and humans, they can also cause severe diseases of the heart liver and the central nervous system.