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Viruses cannot function or reproduce outside a cell, and are totally dependent on a host cell to survive. Most viruses are species specific, and related viruses typically only infect a narrow range of plants, animals, bacteria, or fungi. [1]
A virus is a tiny infectious agent that reproduces inside the cells of living hosts. When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new
The variety of host cells that a virus can infect is called its host range: this is narrow for viruses specialized to infect only a few species, or broad for viruses capable of infecting many. [13]: 123–124 Viral infections in animals provoke an immune response that usually eliminates the infecting virus.
Why are viruses more active? Viruses need a host to replicate, and they can only survive outside briefly. When people sick with a common cold or COVID-19 cough or sneeze, they let out respiratory ...
Entry, or penetration, is the second step in viral replication. This step is characterized by the virus passing through the plasma membrane of the host cell. The most common way a virus gains entry to the host cell is by receptor-mediated endocytosis, which comes at no energy cost to the virus, only the host cell. Receptor-mediated endocytosis ...
Viruses, however, use a completely different mechanism to cause disease. Upon entry into the host, they can do one of two things. Many times, viral pathogens enter the lytic cycle; this is when the virus inserts its DNA or RNA into the host cell, replicates, and eventually causes the cell to lyse, releasing more viruses into the environment.
Viruses need a suitable environment to survive in. There are many characteristics that control the survival of viruses in water such as temperature, light, pH, salinity, organic matter, suspended solids or sediments, and air–water interfaces.
The spike proteins can occasionally be produced as virus-like particles without the viral core. Therefore, optimal budding and release may be dependent on a coordinated "push-and-pull" action between core and spike, where oligomerization of both components is essential. [6] They may help viruses avoid the host immune system.