Viruses are tiny infectious entities that have no metabolism of their own and can only reproduce within living cells.
DNA viruses
Parvoviridae
Parvoviruses are the smallest DNA viruses (18–28 nm) with single-stranded DNA. They have no envelope, are cubic in shape, and are transmitted via the fecal-oral route. The three main genera are densovirus, parvovirus, and dependovirus.
Papovaviridae
This group includes papilloma, polyoma, and SV40 viruses. They are non-enveloped, contain double-stranded DNA, and cause benign and malignant cell changes. Papillomaviruses are, for example, wart viruses.
Adenoviridae
Adenoviruses contain double-stranded DNA and mainly cause respiratory infections. Keratoconjunctivitis epidemica (“swimming pool conjunctivitis”) is a well-known eye disease caused by these viruses.
Herpesviridae
Herpes viruses have an envelope and a large double-stranded DNA. Well-known examples are the herpes simplex virus (types 1 and 2), the varicella zoster virus (chickenpox), and the Epstein-Barr virus (mononucleosis).
Poxviridae
Poxviruses are among the largest viruses and have a complex structure. They contain over 400 genes. Well-known examples are the variola virus (smallpox) and the monkeypox virus.
RNA viruses
Picornaviridae
Small, non-enveloped RNA viruses with approx. 12 genes. Subgroups include enteroviruses, rhinoviruses, aphthoviruses, and cardioviruses. They cause, for example, colds, hepatitis A, and polio.
Enteroviruses
- Poliomyelitis viruses types 1–3: Polio
- Coxsackie viruses: meningitis, encephalitis
- ECHO viruses: flu-like infections, diarrhea
- Hepatitis A virus: hepatitis A
Rhinoviruses
Most common cause of the common cold, not acid-stable, over 115 serotypes known.
Reoviridae
Cause gastrointestinal infections (mainly through rotaviruses) and respiratory diseases. The Colorado tick fever virus is also a representative of this family.
Paramyxoviridae
- Parainfluenza viruses: Respiratory infections
- Mumps virus: Mumps
- Measles virus: Measles
- RS virus: Pseudocroup
Rhabdoviridae
Projectile-shaped viruses with an envelope. The rabies virus (lyssavirus) always leads to death if left untreated.
Coronaviridae
Enveloped viruses with typical “spikes.” Causes respiratory infections and gastrointestinal diseases. The SARS pathogen also belongs to this family.
Retroviridae
Contain RNA and the enzyme reverse transcriptase, which converts RNA into DNA. Most important representatives:
- Spumavirinae: no known pathogenicity to date
- Oncovirinae: can cause cancer (e.g., HTLV)
- Lentivirinae: slow disease progression, e.g., HIV → AIDS
English (United Kingdom)