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When villagers ate the brain, they contracted the disease and then spread it to other villagers who ate their infected brains. [5] While the Fore people stopped eating human meat in the early 1960s, when this was first speculated as the cause, the disease lingered due to kuru's long incubation period of anywhere from 10 to over 50 years. [6]
Some viruses can "hide" within a cell, which may mean that they evade the host cell defenses or immune system and may increase the long-term "success" of the virus. This hiding is deemed latency. During this time, the virus does not produce any progeny, it remains inactive until external stimuli—such as light or stress—prompts it to activate.
Many latent and asymptomatic viruses are present in the human body all the time. Viruses infect all life forms; therefore the bacterial, plant, and animal cells and material in the gut also carry viruses. [6] When viruses cause harm by infecting the cells in the body, a symptomatic disease may develop.
Viruses with no viral envelope enter the cell generally through endocytosis; they “trick” the host cell to ingest the virions through the cell membrane. Cells can take in resources from the environment outside of the cell, and these mechanisms may be exploited by viruses to enter a cell in the same manner as ordinary resources.
Plants have a rigid cell wall made of cellulose, and fungi one of chitin, so most viruses can get inside these cells only after trauma to the cell wall. [ 6 ] : 70 Nearly all plant viruses (such as tobacco mosaic virus) can also move directly from cell to cell, in the form of single-stranded nucleoprotein complexes, through pores called ...
Called zoonotic viruses, they spill over from animals to humans, who can then transmit them to other humans. Liberian Red Cross "burial" team, in Monrovia, Liberia, on October 14, 2014.
B cells, a type of white blood cell, produce antibodies that bind to influenza antigens HA and NA (or HEF [26]) and other proteins to a lesser degree. Once bound to these proteins, antibodies block virions from binding to cellular receptors, neutralizing the virus. In humans, a sizeable antibody response occurs about one week after viral ...
Life-cycle of a typical virus (left to right); following infection of a cell by a single virus, hundreds of offspring are released. When a virus infects a cell, the virus forces it to make thousands more viruses. It does this by making the cell copy the virus's DNA or RNA, making viral proteins, which all assemble to form new virus particles. [37]