What is infectious disease?

1. Infectious Diseases
By: Lecturer Abdullah
Sahar

2. Course Policy of Infectious & TB
Week
Hour
Topic Note
Theory Practical
1 1 1
General information about infectious disease:-
History, infection, infectious processes, faith of
infection in human body, clinical stages of , differences
of infectious diseases from nine infectious diseases,
nomenclature of infectious disease, complications.
2 1 1
Enteric Fever: - Definition, Etiologic agent,
Epidemiology, Pathogenesis and pathology, Clinical
manifestation, Complication, Diagnosis, Treatment,
Prevention. Viral
3 1 1
Hepatitis: - General information, Etiologic agent,
Epidemiology, Pathogenesis and pathology, Clinical
manifestation, Complication, Diagnosis, Treatment,
Prevention.
4 1 1
Amebiasis:- Definition, Transmission and life cycle,
Epidemiology , Classification, Pathogenesis and
pathology, Clinical syndromes, Complications,
Laboratory findings, Differential Diagnosis , Treatment,
Prevention.
5 1 1
Influenza:-Definition, Etiologic agent, Epidemiology,
Pathogenesis and Immunity, Clinical manifestation,
Complications, laboratory findings and
Diagnosis ,Differential Diagnosis ,Treatment,
Prophylaxis.
6 1 1
Diphtheria:- Definition, Etiologic Immunity,
Epidemiology, Pathogenesis and pathology, Clinical
manifestation, Complication, Prognosis, Diagnosis ,
Management, Prevention.
7 1 1
Meningococcal Diseases: - Definition, Etiology,
Epidemiology, Pathogenesis, Classification, Clinical
manifestations, Meningococcemia, Meningitis,
Diagnosis, Treatment, Prognosis, Prevention.
8 1 1
Malaria: - Definition, Etiology and Pathogenesis,
Shizogony, Sporogony, Epidemiology, Clinical
manifestation, Sever malaria, Complications,
Diagnosis, Treatment, Prevention briefly.

3. 9 1 1
History of Tuberculosis
Brief history of TB in Afghanistan and world, Scientific
progress and views during the different civilizations,
Etiology, Agent and characteristics, typical and atypical
mycobacterium, isolation of BK, methods of eradication,
TB pathogens, routes of spread, development of the
disease, course of infection in the organism
10 1 1
Classifications and primary forms of TB
Clinical and epidemiological classification, Primary form
of TB, Primary forms of TB including the primary and
chronic intoxications, Bronchoadenitis, Primary complex
of TB (definition, Pathogenesis, Clinical feature,
diagnosis, differential diagnosis, course and
complications, treatment)
11 1 1
Secondary form of TB, Disseminated pulmonary TB
Endogenic, Exogenic and exogenic super infection foci,
disseminated pulmonary TB, Acute disseminated
pulmonary TB or Miliary TB : (Definition,
Pathogenesis, Predisposing factors, Clinical forms and
features, Differential diagnosis, Complication,
Treatment)
Sub acute disseminated pulmonary TB: (Definition,
Clinical features, Differential diagnosis, Treatment)
Chronic disseminated pulmonary TB: (Definition,
Pathogenesis, Clinical features, Diagnosis, Differential
diagnosis, Treatment)
12 1 1
Focal, infiltrative and Fibro cavernous TB
Focal TB : Definition, Clinical forms, Clinical features,
Diagnosis, Differential diagnosis, Treatment
Infiltrative TB: Definition, Pathogenesis, Clinical forms,
Clinical features, Differential diagnosis, Course and
prognosis, Treatment
Fibro cavernous TB: Definition, Pathogenesis, Clinical
features, Diagnosis, Differential diagnosis, Course and
complications, Treatment
13 1 1
Tuberculosis of the mouth, Pharynx, Larynx and TB
pleurisy
TB of the Mouth : Pathogenesis, Clinical forms,
Clinical features, Differential diagnosis, Treatment
TB of the Pharynx : Pathogenesis, Clinical features,
Diagnosis, Treatment
TB of the Larynx : Pathogenesis, Clinical features,
Diagnosis, Treatment

4. 9 1 1
History of Tuberculosis
Brief history of TB in Afghanistan and world, Scientific
progress and views during the different civilizations,
Etiology, Agent and characteristics, typical and atypical
mycobacterium, isolation of BK, methods of eradication,
TB pathogens, routes of spread, development of the
disease, course of infection in the organism
10 1 1
Classifications and primary forms of TB
Clinical and epidemiological classification, Primary form
of TB, Primary forms of TB including the primary and
chronic intoxications, Bronchoadenitis, Primary complex
of TB (definition, Pathogenesis, Clinical feature,
diagnosis, differential diagnosis, course and
complications, treatment)
11 1 1
Secondary form of TB, Disseminated pulmonary TB
Endogenic, Exogenic and exogenic super infection foci,
disseminated pulmonary TB, Acute disseminated
pulmonary TB or Miliary TB : (Definition,
Pathogenesis, Predisposing factors, Clinical forms and
features, Differential diagnosis, Complication,
Treatment)
Sub acute disseminated pulmonary TB: (Definition,
Clinical features, Differential diagnosis, Treatment)
Chronic disseminated pulmonary TB: (Definition,
Pathogenesis, Clinical features, Diagnosis, Differential
diagnosis, Treatment)
12 1 1
Focal, infiltrative and Fibro cavernous TB
Focal TB : Definition, Clinical forms, Clinical features,
Diagnosis, Differential diagnosis, Treatment
Infiltrative TB: Definition, Pathogenesis, Clinical forms,
Clinical features, Differential diagnosis, Course and
prognosis, Treatment
Fibro cavernous TB: Definition, Pathogenesis, Clinical
features, Diagnosis, Differential diagnosis, Course and
complications, Treatment
13 1 1
Tuberculosis of the mouth, Pharynx, Larynx and TB
pleurisy
TB of the Mouth : Pathogenesis, Clinical forms,
Clinical features, Differential diagnosis, Treatment
TB of the Pharynx : Pathogenesis, Clinical features,
Diagnosis, Treatment
TB of the Larynx : Pathogenesis, Clinical features,
Diagnosis, Treatment

5. 14 1 1
Treatment of TB
Principles of treatment for TB patients, Objectives,
Specific or antibacterial treatments, Non specific or
pathogenic and symptomatic treatment
15 1 1
Prophylaxis and TB control program BCG
Vaccination
What is BCG, Preadministration preparations,
Administration and stages of prophylaxis, Complication,
Contraindication, Chemoprophylaxis ( Definition,
Primary and Secondary chemoprophylaxis, Qualified
groups, Period and Method, Epidemiological sanitary
achievements, Epidemiology and epidemiologic
parameter, National campaign against TB in the country
16 1 1
Case Finding and ambulatory treatments
Methods of case finding, Doctor's duty in different
branches in connection to case finding, Ambulatory
treatments, DOTS and treatment regimens, Standard
treatments

11. Infectious Diseases
By: Lecturer Abdullah Sahar

12. Infectious Diseases - Definitions
 Disease – a pathological condition of body parts or tissues
characterized by an identifiable group of signs and symptoms.
 Infectious disease – disease caused by an infectious agent such as a
bacterium, virus, protozoan, or fungus that can be passed on to others.
 Infection – occurs when an infectious agent enters the body and
begins to reproduce; may or may not lead to disease.
 Pathogen – an infectious agent that causes disease.
 Host – an organism infected by another organism.
 Virulence – the relative ability of an agent to cause rapid and severe
disease in a host.

13. Infectious Diseases as a Cause of Death
 Infectious diseases are responsible for a quarter to a
third of all deaths worldwide.
 Infectious diseases account for more than half of all
deaths in children under the age of 5.
 Of the top ten causes of death compiled by the World
Health Organization, five are due to infectious diseases.
 The top single agent killers are HIV/AIDS, malaria and
tuberculosis. The other top killers are lower respiratory
infections and diarrheal diseases, which are caused by a
variety of agents.

14. Infectious Diseases Throughout History
 Infectious agents have probably always caused
disease in humans.
 Smallpox has been described in ancient Egyptian and
Chinese writings and may have been responsible for
more deaths than all other infectious diseases
combined.
 There is evidence that malaria and poliomyelitis have
existed since ancient times.
 In the 14th Century, the bubonic plague, or Black
Death, killed about 20 million people in Europe alone.
 In the 20th Century, the 1918 influenza may have
killed up to 50 million people worldwide
 Close to 20 million people have died of AIDS to date.
Courtesy of CDC
Recreated 1918 Influenza
virions. The 1918
Spanish flu killed more
than 500,000 people in
the United States and up
to 50 million worldwide.

15. Koch’s Postulates
 Koch developed four criteria to demon-
strate that a specific disease is caused by
a particular agent.
1. The specific agent must be associated
with every case of the disease.
2. The agent must be isolated from a diseased
host and grown in culture.
3. When the culture-grown agent is introduced
into a healthy susceptible host, the agent must
cause the same disease.
4. The same agent must again be isolated from
the infected experimental host.

16. Infectious Disease Agents
 Most infectious agents that cause disease
are microscopic in size and thus, are
called microbes or microorganisms.
 Different groups of agents that cause
disease are:
 Bacteria
 Viruses
 Protozoa (Protists)
 Fungi
 Helminths (Animals)
Courtesy of CDC

17. Transmission of Infectious Diseases
 Agents that cause infectious diseases
can be transmitted in many ways.
 Through the air
 Through contaminated food or
water
 Through body fluids
 By direct contact with contaminated
objects
 By animal vectors such as insects,
birds, bats, etc.
Courtesy of VOA
Chinese students
wearing masks during a
SARS outbreak
Courtesy of CDC
Aedes aegypti mosquito
Known to transmit
Dengue fever

18. Phases of Infectious Disease
 Incubation period – time between infection and the
appearance of signs and symptoms.
 Prodromal phase – mild, nonspecific symptoms that
signal onset of some diseases.
 Clinical phase – a person experiences typical signs and
symptoms of disease.
 Decline phase - subsidence of symptoms.
 Recovery phase – symptoms have disappeared, tissues
heal, and the body regains strength.

19. Classification of Infectious Disease
 By duration
 Acute – develops and runs its course quickly.
 Chronic – develops more slowly and is usually less severe, but may
persist for a long, indefinite period of time.
 Latent – characterized by periods of no symptoms between
outbreaks of illness.
 By location
 Local – confined to a specific area of the body.
 Systemic – a generalized illness that infects most of the body with
pathogens distributed widely in tissues.
 By timing
 Primary – initial infection in a previously healthy person.
 Secondary – infection that occurs in a person weakened by a
primary infection.

20. How Infectious Agents Cause Disease
 Production of poisons, such as
toxins and enzymes, that destroy
cells and tissues.
 Direct invasion and destruction of
host cells.
 Triggering responses from the
host’s immune system leading to
disease signs and symptoms.
Courtesy of CDC
Human
Immunodeficiency Virus.
HIV-1 virions can be seen
on surface of
lymphocytes.

21. Example of an Infectious Disease - Flu
 Acute contagious disease caused by the influenza virus.
 Respiratory tract infection, but symptoms felt
throughout entire body.
 Epidemics occur seasonally with low fatality; more
deadly pandemics occur several times each century.
 Highly changeable virus that can infect multiple
species, including humans, pigs, and birds.
 Concern exists that current avian flu will lead to a new
pandemic.

22. Example of an Infectious Disease - AIDS
 AIDS (Acquired Immune Deficiency
Syndrome) is the disease caused by the
virus called HIV (human
immunodeficiency virus).
 HIV attacks cells of the immune system
and destroys their ability to fight
infection by other agents.
 HIV is spread through the direct
exchange of body fluids.
 There is a long period of time from HIV
infection to the onset of AIDS.
 Anti-HIV drugs prolong the length and
quality of life, but there is no vaccine or
cure for AIDS.
Courtesy of CDC
This highly magnified
transmission electron
micrographic (TEM)
image revealed the
presence of mature forms
of the human virus
immunodeficiency (HIV)
in a tissue sample under
investigation.

23. Reducing the Spread of Infectious Diseases
 Vaccines
 Antimicrobial drugs
 Good personal hygiene and sanitation
 Protection against mosquitoes
 Quarantine

24. Emerging Infectious Diseases
 Emerging diseases are those that have recently
appeared within a population, or whose incidence or
geographic range is increasing rapidly.
 Diseases can emerge or re-emerge due to:
 appearance of a previously unknown agent.
 evolution of a new infectious agent.
 spread of an infectious agent to a new host.
 spread of an infectious agent to new locations.
 acquisition of resistance to anti-microbial drugs.
 deliberate introduction into a population.