infection

What is an infection?
Invasion of a host’s tissues by pathogenic microorganisms such as (viruses ,bacteria, fungi, parasites ,prion)
The organism uses that person s body to sustain itself, reproduce, and colonize. These infectious organisms are known as pathogens.
Some infections are mild and barely noticeable, but others are severe and life-threatening, and some are resistant to treatment.
An infection does not always result in disease.
Microbes can enter the body through the four sites:
1- Respiratory tract (mouth and nose) e.g. influenza virus which causes the flu
2-Gastrointestinal tract (mouth oral cavity) e.g. Vibrio cholerae which causes cholera
-Urogenital tract e.g. Escherichia coli which causes cystitis 3
Breaks in the skin surface e.g. Clostridium tetani which causes tetanus - 4
A disease may cause by:
– Microbial multiplication:
– Toxins(Exo & endotoxins)
– Host response(Autoimmune &Hypersensitivity diseases)
Modes of pathogen transmission
:1- Horizontal transmission
a-Contact
• Direct infectious diseases are commonly transmitted through direct person-to-person contact when an infected person touches or exchanges body fluids with someone else. Sexually transmitted diseases (STDs) can be transmitted this way.
• Indirect (coughing and sneezing)-FLU AND TB
• Vectors (insects) ex:((malaria transformed by anopheles))
b-Inhalation
• aerosols or droplets transmission has been defined as person-to-person transmission of pathogens through the air by means of inhalation of infectious particles)
c-Ingestion (faecal-oral transmission or ingestion of contaminated water or food)

2-Vertical transmission
Mother to child, before birth (HBV& Rubella) or at and after birth(HIV&S.typhi)-
How do people get infections?
Infection can be transmitted in a variety of ways:
These include skin contact, body fluids(STDs), contact with feces(HAV), airborne particles(TB) ,transmission from animal products to human(zoonotic disease-anthrax & toxoplasmosis)) and touching an object that an infected person has also touched.