A virus is a creepy half-live, single strand or double strand of DNA or RNA or both, looking for a cell to invade. A virus has no cell membrane, no metabolism, no respiration and cannot replicate outside of a living cell.
Many dangerous viral strains have been found to originate in China jumping from birds or pigs to the human population. This belief is based on the dense population of humans living in close proximity to high populations of animals. We often hear that many dangerous strains of influenza begin in China. More people died in this one-year pandemic than the four years of the bubonic plague. Unlike previous flu pandemics and epidemics, this flu strain killed healthy adults, whereas most flu strains targeted children, the elderly, and the infirmed. Estimates of the dead range from 20-100 million, up to 5% of the population–all within one year. In 1918 the Spanish flu pandemic was a global killer. New strains can present a clear threat to human survival. Scientists used to think human viruses do not affect animals and animal viruses do not affect humans, but we now know that viruses not only jump species, sometimes they combine to create new strains. We have identified more than 2,000 viruses, though only 10% infect humans.
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