Editing Virology (section)

===Growth in cultures===
Viruses are obligate intracellular parasites and because they only reproduce inside the living cells of a host these cells are needed to grow them in the laboratory. For viruses that infect animals (usually called "animal viruses") cells grown in laboratory [[cell culture]]s are used. In the past, fertile hens' eggs were used and the viruses were grown on the membranes surrounding the embryo. This method is still used in the manufacture of some vaccines. For the viruses that infect bacteria, the [[bacteriophages]], the bacteria growing in test tubes can be used directly. For plant viruses, the natural host plants can be used or, particularly when the infection is not obvious, so-called indicator plants, which show signs of infection more clearly.<ref name="pmid19653216">{{cite journal |vauthors=Liu JZ, Richerson K, Nelson RS |title=Growth conditions for plant virus-host studies |journal=Current Protocols in Microbiology |volume=Chapter 16 |issue= |pages=Unit16A.1 |date=August 2009 |pmid=19653216 |doi=10.1002/9780471729259.mc16a01s14 |s2cid=41236532 |url=}}</ref><ref name="pmid35050076">{{cite journal |vauthors=Valmonte-Cortes GR, Lilly ST, Pearson MN, [[Colleen Higgins|Higgins CM]], MacDiarmid RM |date=January 2022 |title=The Potential of Molecular Indicators of Plant Virus Infection: Are Plants Able to Tell Us They Are Infected? |url= |journal=Plants |volume=11 |issue=2 |page=188 |doi=10.3390/plants11020188 |pmc=8777591 |pmid=35050076 |doi-access=free}}</ref>
[[File:CPE rounding.jpg|right|thumb|Cytopathic effect of herpes simplex virus. The infected cells have become round and balloon-like.]]
Viruses that have grown in cell cultures can be indirectly detected by the detrimental effect they have on the host cell. These [[cytopathic effect]]s are often characteristic of the type of virus. For instance, [[herpes simplex virus]]es produce a characteristic "ballooning" of the cells, typically human [[fibroblast]]s. Some viruses, such as [[mumps virus]] cause red blood cells from chickens to firmly attach to the infected cells. This is called "haemadsorption" or "hemadsorption". Some viruses produce localised "lesions" in cell layers called [[Viral plaque|plaques]], which are useful in quantitation assays and in identifying the species of virus by [[plaque forming units|plaque reduction assays]].<ref name="pmid24899440">{{cite book |vauthors=Gauger PC, Vincent AL |chapter=Serum Virus Neutralization Assay for Detection and Quantitation of Serum-Neutralizing Antibodies to Influenza a Virus in Swine |title=Animal Influenza Virus |series=Methods in Molecular Biology |volume=1161 |pages=313–24 |date=2014 |pmid=24899440 |doi=10.1007/978-1-4939-0758-8_26 |isbn=978-1-4939-0757-1 |chapter-url=}}</ref><ref name="pmid32367358">{{cite book |vauthors=Dimitrova K, Mendoza EJ, Mueller N, Wood H |title=Zika Virus |chapter=A Plaque Reduction Neutralization Test for the Detection of ZIKV-Specific Antibodies |series=Methods in Molecular Biology |volume=2142 |pages=59–71 |date=2020 |pmid=32367358 |doi=10.1007/978-1-0716-0581-3_5 |isbn=978-1-0716-0580-6 |s2cid=218504421 |chapter-url=}}</ref>

Viruses growing in cell cultures are used to measure their susceptibility to validated and novel [[antiviral drug]]s.<ref name="pmid32056049">{{cite journal |vauthors=Lampejo T |title=Influenza and antiviral resistance: an overview |journal=European Journal of Clinical Microbiology & Infectious Diseases |volume=39 |issue=7 |pages=1201–1208 |date=July 2020 |pmid=32056049 |pmc=7223162 |doi=10.1007/s10096-020-03840-9 |url=}}</ref>