INFECTION (Introduction)

Definition: An infection is the invasion of an organism’s body tissues
by disease-causing agents, their multiplication, and the reaction of host
tissues to the infectious agents and the toxins they produce.

An infectious disease, also known as transmissible disease or
communicable disease is an illness resulting from an infection.

Infections can be caused by a wide range of pathogens, most prominently
bacteria and viruses. Mammalian hosts react to infections with an innate
response, often involving inflammation, followed by an adaptive response.

TYPES OF INFECTION

Infections are caused by infectious agents (pathogen) including:

1.    
Bacteria (mycobacterium tuberculosis,
Staphylococcus aureus, Escherichia coli, Clostridium botulinum and Salmonella
spp)

2.    
Viruses and related agents such as viroid
(HIV, Rhinovirus, Lyssaviruses such as rabies virus, Ebola virus and severe
acute respiratory syndrome, coronavirus 2)

3.    
Fungi: this is further subclassified into:

·       
Ascomycota, including yeasts such as
candida, filamentous fungi such as aspergillums, pneumocystis species and
dermatophytes, a group of organisms causing infection of the skin and other
superficial structures in human

·       
Basidiomycota, including the human
pathogenic genic cryptococcus.

 

4.    
Prions (although they don’t secrete
toxins)

5.    
Parasites, which are usually divided into
the following:

·       
Unicellular organisms (malaria,
toxoplasma, babesia)

·       
Macro parasites (worms or helminths)
including nematode such as parasitic roundworms and pinworms, tapeworms
(cestodes) and flukes (trematodes such as schistosomiasis)

6.    
Arthropods such as ticks, mites, fleas and
lice can also cause human disease which conceptually are similar to infections
but invasion of a human or animal body by these macro parasites is usually
termed infestation

Diseases
caused by helminths, which are also macro parasites are sometimes termed
infestation as well, but sometimes called infections)