Q.Poliomyelitis which causes infantile paralysis enters the body through………. a) Skin b) Mouth and nose c) Ears d) Eyes

Viruses are the smallest obligate intracellular parasites — they show no properties of life outside a host cell, but once inside one they force it to manufacture new virus particles, which then burst out (killing that cell) and go on to infect further cells, producing disease.

Viral diseases are grouped into four types by the body system chiefly affected: pneumotropic (respiratory tract — e.g. influenza), dermotropic (skin/subcutaneous tissue — e.g. chicken pox, measles), viscerotropic (blood and visceral organs — e.g. dengue, yellow fever), and neurotropic (central nervous system — e.g. rabies, polio). Eight common viral diseases are tabulated with causative agent, site, transmission and symptoms: common cold (Rhino viruses, respiratory tract, droplet), mumps (Mumps/Paramyxo virus, salivary glands, saliva/droplet), measles (Rubella/Paramyxo virus, skin and respiratory tract, droplet), viral hepatitis (Hepatitis-B virus, liver, parenteral/blood transfusion), chicken pox (Varicella-Zoster virus, respiratory tract/skin/nervous system, droplet and direct contact), poliomyelitis (Polio virus, intestine/brain/spinal cord, droplet via faecal-oral route), dengue fever (Dengue/Flavi virus, skin and blood, Aedes aegypti mosquito), and chikungunya (Alpha/Toga virus, nervous syste …