About Infectious Disease

Infectious diseases are diseases that are caused by certain pathogens – microorganisms (microbes) also known as infectious agents or, more commonly, germs.

They are usually contagious, meaning that they can be transmitted from one person to another or from one species of plant or animal to another

Worms

Bacteria

Viruses

The mechanisms by which they are transmitted are:

Contact with aerosolized droplets – these droplets are spread by sneezing, coughing, talking, kissing and singing.

Eating contaminated food and drinking contaminated water.

Contact with bodily fluids

Contact with contaminated objects, for example a coin passed from one person to another – some diseases penetrate the skin directly

Biological Vectors (more later)

Mechanical Vectors (more later)

The mechanisms by which they are transmitted are:

Contact with aerosolized droplets – these droplets are spread by sneezing, coughing, talking, kissing and singing.

Eating contaminated food and drinking contaminated water.

Contact with bodily fluids

Contact with contaminated objects, for example a coin passed from one person to another – some diseases penetrate the skin directly

Biological Vectors (more later)

Mechanical Vectors (more later)

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

The mechanisms by which they are transmitted are:

Contact with aerosolized droplets – these droplets are spread by sneezing, coughing, talking, kissing and singing.

Eating contaminated food and drinking contaminated water.

Contact with bodily fluids

Contact with contaminated objects, for example a coin passed from one person to another – some diseases penetrate the skin directly

Biological Vectors (more later)

Mechanical Vectors (more later)

The mechanisms by which they are transmitted are:

Contact with aerosolized droplets – these droplets are spread by sneezing, coughing, talking, kissing and singing.

Eating contaminated food and drinking contaminated water.

Contact with bodily fluids

Contact with contaminated objects, for example a coin passed from one person to another – some diseases penetrate the skin directly

Biological Vectors (more later)

Mechanical Vectors (more later)

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

Infecting agents are transmitted by:

Physical contact with an infected individual

Liquids

Food

Body Fluids

Contaminated objects

Airborne inhalation

Vector – borne spread.

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:

Sporadic: occasional occurrenceEndemic: cases in a region are regular and oftenEpidemic: unusually high number of cases in a regionPandemic: 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:

Sporadic: occasional occurrenceEndemic: cases in a region are regular and oftenEpidemic: unusually high number of cases in a regionPandemic: global epidemic

Transmission of an infectious disease depends on a number of factors:

Virulence: the ability of a pathogen/infecting agent to cause diseaseThe distance that is travelled by infected peopleHow 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:

Sporadic: occasional occurrenceEndemic: cases in a region are regular and oftenEpidemic: unusually high number of cases in a regionPandemic: global epidemic

Transmission of an infectious disease depends on a number of factors:

Virulence: the ability of a pathogen/infecting agent to cause diseaseThe distance that is travelled by infected peopleHow contagious the disease isSmall-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 DiseaseMicrobial 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

Microscopy – can be a simple compound light microscope or an advanced electron microscope

Biochemical Tests – used to test for infections like strep throat

Molecular Diagnostics – used to test for infections like tetanus

Testing for infectious DiseaseMicrobial 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

Microscopy – can be a simple compound light microscope or an advanced electron microscope

Biochemical Tests – used to test for infections like strep throat

Molecular Diagnostics – used to test for infections like tetanus

Clearance

Immune mechanisms kill or inactivate the inoculums of the pathogen.

Antibodies and/or T lymphocytes mediate immunity against infectious diseases by having a direct effect on the pathogen

Neutralising viruses – they can no longer enter cells to cause harm

Kill the infected cell so that the disease cannot spread from this cell.

Testing for infectious DiseaseMicrobial 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

Microscopy – can be a simple compound light microscope or an advanced electron microscope

Biochemical Tests – used to test for infections like strep throat

Molecular Diagnostics – used to test for infections like tetanus

Clearance

Immune mechanisms kill or inactivate the inoculums of the pathogen.

Antibodies and/or T lymphocytes mediate immunity against infectious diseases by having a direct effect on the pathogen

Neutralising viruses – they can no longer enter cells to cause harm

Kill the infected cell so that the disease cannot spread from this cell.

Immunity:

Resistance to infection may be acquired:Following a disease Asymptomatic (symptom free) carriage of the pathogenHarbouring an organism with a similar structure – cross-reactingVaccination

Source: http://en.wikipedia.org/wiki/Infectious_disease