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In general, viral infections are systemic. This means they involve many different parts of the body or more than one body system at the same time; i.e. a runny nose, sinus congestion, cough, body aches etc. They can be local at times as in viral conjunctivitis or "pink eye" and herpes. Only a few viral infections are painful, like herpes. The ...
The immune system is involved in many aspects of physiological regulation in the body. The immune system interacts intimately with other systems, such as the endocrine [83] [84] and the nervous [85] [86] [87] systems. The immune system also plays a crucial role in embryogenesis (development of the embryo), as well as in tissue repair and ...
Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell and introduces viral material into the cell. The major steps involved in viral entry are shown below. [1] Despite the variation among viruses, there are several shared generalities concerning viral entry. [2]
Tuberculosis generally affects the lungs, but it can also affect other parts of the body. [1] Most infections show no symptoms, in which case it is known as latent tuberculosis . [ 1 ] Around 10% of latent infections progress to active disease that, if left untreated, kill about half of those affected. [ 1 ]
Common symptoms present in the different types of leprosy include a runny nose; dry scalp; eye problems; skin lesions; muscle weakness; reddish skin; smooth, shiny, diffuse thickening of facial skin, ear, and hand; loss of sensation in fingers and toes; thickening of peripheral nerves; a flat nose from the destruction of nasal cartilages; and changes in phonation and other aspects of speech ...
First, it can survive the highly acidic conditions of the stomach, allowing ingested viruses to infect the host and spread throughout the body via the lymphatic system. [3] Second, because it can replicate very quickly, the virus overwhelms the host's organs before an immune response can be mounted. [ 52 ]
The ability of bacteria to cause disease is described in terms of the number of infecting bacteria, the route of entry into the body, the effects of host defense mechanisms, and intrinsic characteristics of the bacteria called virulence factors.
Virulence involves pathogens extracting host nutrients for their survival, evading host immune systems by producing microbial toxins and causing immunosuppression. Optimal virulence describes a theorized equilibrium between a pathogen spreading to additional hosts to parasitize resources, while lowering their virulence to keep hosts living for ...