This document discusses different types of diseases in microbiology. There are four main types: infectious diseases which are caused by microbes like viruses and bacteria; communicable diseases which spread between people; non-communicable diseases which are chronic like cancer and heart disease; and contagious diseases which spread through direct or indirect contact. Infectious diseases can be infectious, acute, chronic, or subclinical. Diseases spread through stages including a reservoir, exit portal, entry portal, and transmission between hosts.

1. “Disease and its types in
Microbiology”
Taufica Nusrat
MS in Biotechnology
Institute of biotechnology and genetic engineering

2. Disease:
Disease, is any harmful deviation from the normal structural or
functional state of an organism, generally associated with certain signs
and symptoms and differing in nature from physical injury.
Types of Disease in Microbiology:
There are four main type of disease,
(1)Infectious disease
(2)Communicable disease
(3)Non-communicable disease
(4)Contagious disease

3. 1)Infectious disease:
Infectious diseases are diseases caused by living organisms like viruses and bacteria. They
can be passed from person to person through body secretions, insects or other means.
Examples are SARS, influenza, the common cold, tuberculosis (TB), Hepatitis A and B.
(2)Communicable disease:
A communicable disease is one that is spread from one person to another through a
variety of ways that include: contact with blood and bodily fluids; breathing in an airborne
virus; or by being bitten by an insect.
Some examples of the reportable communicable diseases include Hepatitis A, B & C,
influenza, measles, and salmonella and other food borne illnesses.
Types of Disease

4. Types of Disease
(3) Non-communicable disease
Non-communicable diseases generally are long-lasting and progress
slowly, and thus they are sometimes also referred to as chronic
diseases. They can arise from environmental exposures or from
genetically determined abnormalities, which may be evident at birth or
which may become apparent later in life.
cancer, cardiovascular disease (e.g., heart attack, stroke),
chronic respiratory disease (e.g., asthma), and diabetes mellitus.

5. Types of Disease
(4) Contagious disease:
Contagious diseases (such as the flu, colds, or strep throat) spread from
person to person in several ways. One way is through direct physical
contact, like touching or kissing a person who has the infection.
Another way is when an infectious microbe travels through the air after
someone nearby sneezes or coughs.

6. Common terminology
• Acute Infection: An infection characterized by sudden onset, rapid progression, and often
with severe symptoms.
• Chronic Infection: An infection characterized by delayed onset and slow progression.
• Subacute or chronic viral infection: They tend to progress slowly over months or years
rather than weeks or days. The incubation period is often longer. Reactivation of a latent infection in
an immunocompromised host is responsible in some of them.
• Rubella virus Progressive rubella panencephalitis
• Subclinical infection: An infection with few or no obvious symptoms.

7. Common terminology
• Local: Infection that is limited to a defined area or single organ with symptoms that resemble
inflammation (redness, tenderness and swelling.) A local infection, like a urinary tract infection, pneumonia, or
an infected cut, the signs and symptoms are localized according to the area affected.
• Focal: Focal infection theory is the concept that a local bacterial infection influencing a little part of the
human body such as decaying teeth, tooth roots, infected periodontal tissues that may cause subsequent
bacterial infections in other areas of the human body such as eye balls, kidneys.
• Systematic infection: An infection that has spread to several regions or areas in the body of the host.
• Septicemia: Acute illness caused by infectious agents or their products circulating in the blood stream.

8. Common terminology
• Bacteremia: Bacteria circulation in the bloodstream
• Viremia: Viruses is circulation in the bloodstream
• Toxemia: Toxin circulating in the bloodstream

9. Types of Infection:
Primary infection: An infection that develops in an otherwise healthy
individual. A primary disease is a disease that is due to illness, as opposed to
secondary disease, which is a complication that is caused by the primary disease.
Secondary infection: An infection that develops in an individual who is
already infected with a different pathogen.

10. Types of Infection:
Super infection: A second infection superimposed on an earlier one
especially by a different microbial agent of exogenous or endogenous
origin that is resistant to the treatment used against the first infection.
Mixed infection: In clinical bacteriology a mixed infection is a
single infection is caused by a variety of bacterial species which are
simultaneous causing the same infection. For example: peritonitis
caused by all kinds of different gut bacteria and yeasts.

11. BIOLOGIC CHARACTERISTICS OF INFECTIOUS AGENTS:
• Infectivity – the ability to infect a host.
• Pathogenicity – the ability to cause disease in the host. This term is
often used to describe or compare species.
• Virulence – the ability to cause severe disease in the host specific
microbe – Based on: • Invasive qualities • Toxic qualities • Presence of
pili or fimbriae for adhesion • Ability to avoid host defenses (mutate)
• Immunogenicity –the ability to induce an immune response in the
host Stages of infectious disease.

12. Stages of Infectious Disease:
The development of an infection happens in a cycle that depends on all
elements of the cycle being present. There are six elements in the chain
of infection:

13. Stages of Infectious Disease:
Infectious agent – A microbial organism with the ability to cause
disease. The greater the organism's virulence (ability to grow and
multiply), invasiveness (ability to enter tissue) and pathogenicity (ability
to cause disease), the greater the possibility that the organism will
cause an infection. Infectious agents are bacteria, virus, fungi, and
parasites.
Reservoir – A place within which microorganisms can thrive and
reproduce. For example, microorganisms thrive in human beings,
animals, and inanimate objects such as water, table tops, and
doorknobs.

14. Stages of Infectious Disease:
Portal of exit – A place of exit providing a way for a microorganism to
leave the reservoir. For example, the microorganism may leave the
reservoir through the nose or mouth when someone sneezes or
coughs. Microorganisms, carried away from the body by feces, may also
leave the reservoir of an infected bowel. The number of pathogens that
reach the portal of entry influences the likelihood of successful disease
transmission.

15. Stages of Infectious Disease:
Mode of transmission: Method of transfer by which the organism moves or is
carried from one place to another.
Route Example Disease
Direct contact Kissing , sexual contact, Skin to skin
contact
STD, Skin infection, Scabies
Droplet Organism on large respiratory
droplets that people sneeze, cough,
drip or exhale. Disease spread when
people are close to each other and
inhale droplet.
Mumps, common cold, meningitis.
Indirect contact Contact with contaminated surface,
clothing etc.
Skin infection, diarrheal disease
Vehicle Eat or drink contaminated food
transfused infected blood.
Hepatitis b, Hepatitis c
Airborne Organism on dust particle or small
respiratory droplets that may become
aerosolized when people sneeze or
cough.
Chicken pox or small pox.
Vector Bite from disease carrying ticks, fleas,
mosquitoes.
Lyme disease

16. Stages of Infectious Disease:
Portal of entry – An opening allowing the microorganism to enter the
host. Portals include body orifices, mucus membranes, or breaks in the
skin. Portals also result from tubes placed in body cavities, such as
urinary catheters, or from punctures produced by invasive procedures
such as intravenous fluid replacement.
Host – A person who cannot resist a microorganism invading the body,
multiplying, and resulting in infection. The host is susceptible to the
disease, lacking immunity or physical resistance to overcome the
invasion by the pathogenic microorganism.

17. Stages of Infectious Disease:
Bacterial pathogenesis occur in most common forms: Production of toxins:

18. Stages of Infectious Disease:
Finally, pathogens leave the body and return to a
reservoir or enter a new host.

19. Thank you!