a brief over view of acute diseases and pathogens

1. Bacteria, viruses and parasites
Microbiology is a term that's applied to the study of micro-organisms. Medical microbiology is a specialist area of medical practice that deals with
pathogenic micro-organisms - that is the pathogens that cause disease among humans. While microbiology technically focuses on the study of
bacteria, it can and typically also encompasses the study of virology and parasites. However, you may come across more specific terminology -
bacteriology (the study of bacteria), virology (the study of viruses) and parasitology (the study of parasites).
The word reservoir in infectious diseases describes the natural population in which a pathogen resides and reproduces. Zoonoses are a group of
infectious diseases that emerge from animals and pass into humans. Zoonoses are diseases where the natural reservoir occurs within animals.
The eight pathogens that were selected in the previous reading represent a spread of these three types of pathogen, manifesting in different types of
disease.

2. Bacteria, viruses and parasites
Pathogen
Pathogen type
(classification)
Primarydisease
manifestation
Main method of transmission
205Campylobact
er jejuni
Bacterium
Gastrointestinal infection -
diarrhoea and vomiting
Contaminated food or water, but also person-to-person spread possible in circumstances where poor hygiene
practices are present
Cryptosporidium
parvum
Parasite
(Protozoal)
Gastrointestinal infection -
diarrhoea and vomiting
Often viadirect or indirect contact with infected animals (zoonosis) but also through infected water (contaminated
with animal faeces); sometimes asymptomatic but problematic among people with impaired immunity.
Escherichia coli Bacterium
Gastrointestinal infection -
predominantly diarrhoea
Zoonotic but also person-to-person transmission possible in more common types. Particularly problematic among
people with impaired immunity.
Hepatovirus A
(also known as
Hepatitis A Virus,
HAV)
Virus
(Picornaviridae)
Hepatitis (inflammation of
the liver)
Person-to-person spread viafaeco-oral route; via sexual transmission and probably viaurine.
Norovirus (also
known as Winter
Vomiting Bug or
Norwalk Virus)
Virus
(Calciviridae)
Gastrointestinal infection -
predominantly vomiting
Person-to-person spread viafaeco-oral route (in particular viadroplet spread from projectile vomiting); also
potentially spread through contaminated food.
Salmonella spp Bacterium
Gastrointestinal infection -
diarrhoea and vomiting
Mostly through contaminated food, but originating from animal reservoirs including domestic animals, birds and
amphibians. Salmonella enterica and Salmonella typhimurium are the most common serotypes. Salmonella
typhi and Salmonella paratyphi are responsible for Typhoid fever and Paratyhoid fever respectively.
Shigella spp Bacterium
Gastrointestinal infection -
diarrhoea and vomiting;
referred to as Shigellosis
Faeco-oral transmission particularly within households and institutional settings from diarrhoea. Occasionally
spread by food and water.

3. Bacteria, viruses and parasites
Vibrio cholerae Bacterium
Gastrointestinal infection -
predominantly diarrhoea
Faeco-oral viawater with the main reservoir in aquatic environments; associated with contaminated shellfish and
raw food washed in contaminated water.