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Contrary to common belief, harmful viruses may be in the minority, compared to benign viruses in the human body. It is much harder to identify viruses than it is to identify bacteria, therefore the understanding of benign viruses in the human body is very rudimentary. [ 2 ]
A human pathogen is a pathogen (microbe or microorganism such as a virus, bacterium, prion, or fungus) that causes disease in humans. The human physiological defense against common pathogens (such as Pneumocystis ) is mainly the responsibility of the immune system with help by some of the body's normal microbiota .
Humans can be infected with many types of pathogens, including prions, viruses, bacteria, and fungi, causing symptoms like sneezing, coughing, fever, vomiting, and potentially lethal organ failure. While some symptoms are caused by the pathogenic infection, others are caused by the immune system's efforts to kill the pathogen, such as ...
An analysis of all the publicly available viral genome sequences yielded a surprising result: humans give more viruses - about twice as many - to animals than they give to us. Of those, 79% ...
The human strains of Ebola virus, for example, incapacitate those infected extremely quickly and kill them soon after. As a result, those affected by this disease do not have the opportunity to travel very far from the initial infection zone. [72] Also, this virus must spread through skin lesions or permeable membranes such as the eye.
The Hepatitis D virus has not yet been assigned to a family, but is clearly distinct from the other families infecting humans. Viruses known to infect humans that have not been associated with disease: the family Anelloviridae and the genus Dependovirus. Both of these taxa are non-enveloped single-stranded DNA viruses.
With the exception of smallpox, most pandemics are caused by newly evolved viruses. These "emergent" viruses are usually mutants of less harmful viruses that have circulated previously either in humans or in other animals. [66] Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) are caused by new types of ...
After a typical human infection by bite, the virus enters the peripheral nervous system. It then travels retrograde along the efferent nerves toward the central nervous system. [57] During this phase, the virus cannot be easily detected within the host, and vaccination may still confer cell-mediated immunity to prevent symptomatic rabies.