About Infectious diseases are diseases that are caused

About ØInfectious diseases are diseases that are caused by certain pathogens – microorganisms (microbes) also known as infectious agents or, more commonly, germs. Infectious Disease Viruses ØThey are usually contagious, meaning that they can be transmitted from one person to another or from one species of plant or animal to another Bacteria Worms

Infecting agents are transmitted by: The mechanisms by which they are transmitted are: Ø Physical contact with an infected individual Ø Contact with aerosolized droplets – these droplets are spread by sneezing, coughing, talking, kissing and singing. Ø Liquids Ø Food Ø Eating contaminated food and drinking contaminated water. Ø Body Fluids Ø Contact with bodily fluids Ø Contaminated objects Ø Contact with contaminated objects, for example a coin passed from one person to another – some diseases penetrate the skin directly Ø Airborne inhalation Ø Vector – borne spread. Ø Biological Vectors (more later) Ø Mechanical Vectors (more later)

Transmission of infectious diseases may also involve a vector. Vectors may be mechanical or biological: Image: “Mosquito” by tanakawho on Flickr.

Transmission of infectious diseases may also involve a vector. Vectors may be mechanical or biological: An example of a mechanical vector is a housefly, which lands on cow dung and then lands on food, which is then eaten. The bacteria travel from the dung to the food without ever actually entering the body of the fly. Image: “Mosquito” by tanakawho on Flickr.

Transmission of infectious diseases may also involve a vector. Vectors may be mechanical or biological: An example of a mechanical vector is a housefly, which lands on cow dung and then lands on food, which is then eaten. The bacteria travel from the dung to the food without ever actually entering the body of the fly. A biological vector has the pathogens within its body, and delivers them to new hosts in an active manner, usually a bite. Mosquitoes, ticks, fleas and lice are examples of biological vectors and are often responsible for serious blood-borne diseases, such as malaria. Image: “Mosquito” by tanakawho on Flickr.

Transmission of infectious diseases may also involve a vector. Vectors may be mechanical or biological: An example of a mechanical vector is a housefly, which lands on cow dung and then lands on food, which is then eaten. The bacteria travel from the dung to the food without ever actually entering the body of the fly. A biological vector has the pathogens within its body, and delivers them to new hosts in an active manner, usually a bite. Mosquitoes, ticks, fleas and lice are examples of biological vectors and are often responsible for serious blood-borne diseases, such as malaria. A common strategy used to control vector borne infectious diseases is to interrupt the life cycle of a pathogen by killing the vector. Image: “Mosquito” by tanakawho on Flickr.

The study of disease in a population is called epidemiology. In the case of infectious disease, epidemiology is used to classify the type of disease outbreak: ØSporadic: occasional occurrence ØEndemic: cases in a region are regular and often ØEpidemic: unusually high number of cases in a region ØPandemic: global epidemic

The study of disease in a population is called epidemiology. In the case of infectious disease, epidemiology is used to classify the type of disease outbreak: ØSporadic: occasional occurrence ØEndemic: cases in a region are regular and often ØEpidemic: unusually high number of cases in a region ØPandemic: global epidemic Transmission of an infectious disease depends on a number of factors: ØVirulence: the ability of a pathogen/infecting agent to cause disease ØThe distance that is travelled by infected people ØHow contagious the disease is

The study of disease in a population is called epidemiology. In the case of infectious disease, epidemiology is used to classify the type of disease outbreak: ØSporadic: occasional occurrence ØEndemic: cases in a region are regular and often ØEpidemic: unusually high number of cases in a region ØPandemic: global epidemic Transmission of an infectious disease depends on a number of factors: ØVirulence: the ability of a pathogen/infecting agent to cause disease ØThe distance that is travelled by infected people ØHow contagious the disease is ØSmall-world Networks – how groups of people interact: a small, relatively isolated group of infected people could infect a large susceptible group of people even if there’s very little interaction between the two groups

Testing for infectious Disease ØMicrobial Culture – growth medium is provided for a specific agent, and a sample taken from potentially diseased tissue or fluid is tested for the presence of an infectious agent able to grow in that medium ØMicroscopy – can be a simple compound light microscope or an advanced electron microscope ØBiochemical Tests – used to test for infections like strep throat ØMolecular Diagnostics – used to test for infections like tetanus

Testing for infectious Disease ØMicrobial Culture – growth medium is provided for a specific agent, and a sample taken from potentially diseased tissue or fluid is tested for the presence of an infectious agent able to grow in that medium Clearance ØImmune mechanisms kill or inactivate the inoculums of the pathogen. ØMicroscopy – can be a simple compound light microscope or an advanced electron microscope ØAntibodies and/or T lymphocytes mediate immunity against infectious diseases by having a direct effect on the pathogen ØBiochemical Tests – used to test for infections like strep throat ØNeutralising viruses – they can no longer enter cells to cause harm ØMolecular Diagnostics – used to test for infections like tetanus ØKill the infected cell so that the disease cannot spread from this cell.

Clearance Testing for infectious Disease ØMicrobial Culture – growth medium is provided for a specific agent, and a sample taken from potentially diseased tissue or fluid is tested for the presence of an infectious agent able to grow in that medium ØImmune mechanisms kill or inactivate the inoculums of the pathogen. ØMicroscopy – can be a simple compound light microscope or an advanced electron microscope ØAntibodies and/or T lymphocytes mediate immunity against infectious diseases by having a direct effect on the pathogen ØBiochemical Tests – used to test for infections like strep throat ØNeutralising viruses – they can no longer enter cells to cause harm ØMolecular Diagnostics – used to test for infections like tetanus ØKill the infected cell so that the disease cannot spread from this cell. Immunity: Resistance to infection may be acquired: ØFollowing a disease ØAsymptomatic (symptom free) carriage of the pathogen ØHarbouring an organism with a similar structure – cross -reacting ØVaccination

1 • Lower Respiratory Infections 2 • HIV/AIDS 3 • Diarrheal Diseases 4 5 • Tuberculosis (TB) • Malaria 6 • Measles 7 • Pertussis 8 • Tetanus 9 • Meningitis 10 • Syphilis Source: http: //en. wikipedia. org/wiki/Infectious_disease