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Viral evolution is an important aspect of the epidemiology of viral diseases such as influenza (influenza virus), AIDS , and hepatitis (e.g. HCV). The rapidity of viral mutation also causes problems in the development of successful vaccines and antiviral drugs , as resistant mutations often appear within weeks or months after the beginning of a ...
New viruses and strains of viruses were discovered in every decade of the second half of the 20th century. These discoveries have continued in the 21st century as new viral diseases such as SARS [72] and nipah virus [73] have emerged. Despite scientists' achievements over the past one hundred years, viruses continue to pose new threats and ...
New groups of viruses might have repeatedly emerged at all stages of the evolution of life. [16] There are three major theories about the origins of viruses: [16] [17] Regressive theory Viruses may have once been small cells that parasitised larger cells. Eventually, the genes they no longer needed for a parasitic way of life were lost.
The passage of virus produces mutations within the viral genome, and hinders the virus's ability to infect nervous tissue. [6] Both vaccines have been used for decades to induce immunity to polio, and to stop the spread of the infection. However, OPV has several advantages; because the vaccine is introduced in the gastrointestinal tract, the ...
The rapid rate of evolution in viruses allows molecular clock models to be estimated from genetic sequences, thus providing a per-year rate of evolution of the virus. With the rate of evolution measured in real units of time, it is possible to infer the date of the most recent common ancestor (MRCA) for a set of viral sequences. The age of the ...
Gamma phage, an example of virus particles (visualised by electron microscopy) Virology is the scientific study of biological viruses.It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity, the diseases they ...
As fewer children die or are debilitated due to measles, mumps, rubella, diphtheria, tetanus and polio, we tend to forget that this is the result of an evidence-based childhood vaccination program.
A founder virus can introduce a different phenotype for the ensuing evolution. Evolution of viruses in nature and as disease agents can be viewed as succession of mutant spectrum alterations, subjected to expansions and reductions of population size in a continuous interplay of positive and negative selection and random drift.