There is an ongoing debate whether viruses can be classified as
life forms as they lack the characteristics (e.g. cell body or autarkic
replication) of eukaryotic or prokaryotic cells. The emergence of
viruses in evolutionary terms is also unclear; it is likely they have
advanced from bacterial plasmids or other parts of nucleic acids.
Virology was founded when Dmitri Ivanovsky and Martinus
Beijerinck discovered plant viruses at the end of the 19th century.
Viruses comprise complex particles that infect bacterial, plant and
animal cells. They are classified by their genome (where ss is
single stranded and ds is double stranded, according to the
Baltimore classification) into dsDNA viruses, ssDNA viruses,
dsRNA viruses, (+)ssRNA viruses, (−)ssRNA viruses, ssRNA-RT
viruses and dsDNA-RT viruses. The classification of the
International Committee on Taxonomy of Viruses (ICTV) divides
virus by their biological properties into orders, families and so on.
The morphologies of viruses are very diverse and comprise
viruses with or without lipid cover and multiple shapes.
As the biological complexity of viruses unfolds, the pulmonary
physician continues to face viral infections in daily practice:
1) typical respiratory viruses, such as influenza, rhinovirus or RSV,
which cause common infectious diseases; 2) new viruses, which
often originate in animals, become a threat to mankind and cause
outbreaks (SARS-CoV and MERS-CoV); 3) immunocompromised
patients who are susceptible to a wide range of viral species (CMV
and herpes simplex virus); and 4) respiratory viruses and newly
identified viruses, which have been shown to impact on the
development of non-communicable diseases, such as asthma,
COPD and perhaps cancer. Viral infections therefore play an
important role in respiratory medicine and are within the main
focus of public health activities.
This ERS Monograph considers viral infections of the respiratory
tract with a focus on newly emerged viruses. There are chapters on
SARS-CoV, MERS-CoV and avian influenza, as well as more
common viral pathogens, such as seasonal influenza and rhinovirus.
Copyright ©ERS 2016. Print ISBN: 978-1-84984-069-9. Online ISBN: 978-1-84984-070-5. Print ISSN: 2312-508X. Online ISSN: 2312-5098.
ERS Monogr 2016; 72: v–vi. DOI: 10.1183/2312508X.10008916 v