- A disease is an illness or disorder of the body or mind that lead to poor health
- Each disease is associated with a set of signs and symptoms
- Infectious diseases are caused by pathogens and are transmissible (can be
spread between individuals within a population)
- Infectious diseases: these are diseases caused by organisms known as
pathogens. They are sometimes called communicable diseases as they are
passed from infected to uninfected people. Some also affect animals and are
passed from animals to humans. (cholera, malaria, HIV)
- Noninfectious disease: these are long term, degenerative diseases that are
not caused by pathogens. (lung cancer, chronic pulmonary disease)
Common Pathogens & Their Diseases
- Four infectious diseases of worldwide importance are cholera, malaria,
tuberculosis and HIV/AIDS
- The number of people infected remains very high and are serious public
health problems.
Disease Causative agent Type of organism
(pathogen)
Transmission of cholera:
- Caused by the bacterium VIbrio cholerae
- The disease is waterborne (bacteria lives in water) and food-borne
- The disease occurs where people do not have access to proper sanitation
and uncontaminated food
, - Cholera can be transmitted when people bath or wash in contaminated water,
drink contaminated water or eat food exposed to contaminated water.
- Infected people egest large numbers of the bacteria in their faeces
- If these faeces contaminate the water supply, or if infected people handle food
or cooking utensils without washing their hands, the bacteria is transmitted to
uninfected people
Transmission of malaria
- Malaria is caused by one of four species of the protoctista plasmodium.
- These protoctista are transmitted to humans by an insect vector (a vector is
an organism that does not cause the disease itself but spreads the disease by
passing on the pathogen from on host organism to another):
- Female Anopheles mosquitoes feed on human blood to obtain the protein
they need to develop their eggs
- If the person they bite is infected with plasmodium, the mosquito will take up
some of the pathogen with the blood meal
- When feeding on the next human, Plasmodium pass from the mosquito to
the new humans blood
- Malaria may also be transmitted during blood transfusion and when unsterile
needles are re used
- Plasmodium can also pass from mother to child across the placenta
-
Transmission of tuberculosis (TB)
- When infected people with the active form of the disease cough or sneeze,
the mycobacterium tuberculosis bacteria enter the air in tiny droplets of liquid
- TB is transmitted when uninfected people then inhale these droplets.
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