What is Infection?

Infection is the invasion and multiplication of microorganisms in or on body tissues that produce signs and symptoms as well as an immune response. Such reproduction injures the host by causing cellular damage from microorganism-produced toxins or intracellular multiplication or by competing with host metabolism. The host's own immune response may compound the tissue damage. The damage may be localized (as in infected pressure ulcers) or systemic. The infection's severity varies with the pathogenicity and number of the invading microorganisms and the strength of host defenses. The very young and the very old are especially susceptible to infections.

Why are the microorganisms that cause infectious diseases so hard to overcome? Many complex reasons exist:

• Some bacteria - especially gram-negative bacillidevelop resistance to antibiotics.
• Some microorganisms - the influenza virus, for example - have so many strains that a single vaccine can't provide protection against them all.
• Most viruses resist antiviral drugs.
• Some microorganisms localize in areas that make treatment difficult, such as the central nervous system or bone.

Moreover, certain factors contribute to increase the risk of infection. For example, travel can expose people to diseases for which they have little. natural immunity. In addition, the expanded use of immunosuppressants, surgery, and other invasive procedures increases the risk of infection.

Kinds of infections

A laboratory-verified infection that causes no signs and symptoms is called a subclinical, silent, or asymptomatic injection. A multiplication of microbes that produces no signs, symptoms, or immune responses is called a colonization. A person with a subclinical infection or a colonization may be a carrier and transmit infection to others.

A latent infection occurs after a microorganism has been dormant in the host, sometimes for years. An exogenous infection results from environmental pathogens; an endogenous infection, from the host's normal flora (for instance, Escherichia coli displaced, from the colon, which may cause urinary tract infection).

The varied forms of microorganisms responsible for infectious diseases include bacteria, spirochetes (a type of bacteria), viruses, rickettsiae, chlamydiae, fungi, and protozoa. Larger organisms, such as helminths (worms), also may cause disease.

© Doctor-clinic.org. All rights reserved.

Disclaimer :- The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor . We will not be liable for any complications or other medical accidents arising from or in connection with the use of or reliance upon any information in this web site.