Download Communicable Disease

COMMUNICABLE
DISEASE
EPIDEMIOLOGY,
CONTROL &
PREVENTION
CHP300
Mohamed M.B. Alnoor
COMMUNICABLE DISEASE
Content
Sources & Channels of infection
Host-parasite relationship
Cycle of infection
Outcome of infection
Disease mechanism
Spectrum of disease
Levels of disease occurrence
Control and prevention of disease
Levels of Prevention
Natural History of disease
COMMUNICABLE DISEASE
DEFINITIONS
COMMUNICABLE DISEASE :
EPIDEMIOLOGY :
CONTROL :
PREVENTION :
COMMUNICABLE DISEASE
DEFINITIONS
Control:
Elimination :
Eradication:
Extinction:
COMMUNICABLE DISEASE
DEFINITIONS
SOURCES OF INFECTION
CASE OF DISEASE : a patient
CARRIER :
. Incubatory carrier
. Convalescent carrier
. Chronic carrier
. In-apparent carrier
ANIMAL RESERVOIR (ZOONOSIS)
INANIMATE RESERVOIR (THE SOIL)
COMMUNICABLE DISEASE
DEFINITIONS
SOURCES OF INFECTION
Reservoir
Zoonosis
animal
animal
human
COMMUNICABLE DISEASE
DEFINITIONS
SOURCES OF INFECTION
Examples:
Neisseria gonorrhea
-Source = humans
-Reservoir = humans
Salmonella typhi
-Source = food/water
-Reservoir = humans
Rabies virus
Hepatitis C
-Source = saliva of
-Source = transfusion,
the dog
blood products
-Reservoir = the dog
-Reservoir = humans
COMMUNICABLE DISEASE
CHANNELS OF
TRANSMISSION OF
INFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
COMMUNICABLE DISEASE
CHANNELS OF
TRANSMISSION OF
INFECTION:
1. Water-washed dis.
(Dis. of skin, eye)
2. Faecal-oral disease.
(Viral, bact., parasitic)
3. Soil -mediated infections. (Tetanus, intestinal parasites)
4. Diseases of water contact. (Bilharzia, Guinea worm)
5. Food-borne dis.
(F.P., intestinal flukes)
6. Infectious skin rashes.
(Chickenpox, smallpox)
7. Respiratory infections.
(Viral, bacterial)
8. Dis. Transmitted via body fluids.
(STD)
9. Insect-borne.
(Viral, parasitic)
10. Zoonoses.
(Brucellosis, rabies)
COMMUNICABLE DISEASE
CHANNELS OF
TRANSMISSION OF
INFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
1. Water-washed dis.
(Dis. of skin, eye)
2. Faecal-oral disease.
(Viral, bact., parasitic)
3. Soil -mediated infections. (Tetanus, intestinal parasites)
4. Diseases of water contact. (Bilharzia, Guinea worm)
5. Food-borne dis.
(F.P., intestinal flukes)
6. Infectious skin rashes.
(Chickenpox, smallpox)
7. Respiratory infections.
(Viral, bacterial)
8. Dis. Transmitted via body fluids.
(STD)
9. Insect-borne.
(Viral, parasitic)
10. Zoonoses.
(Brucellosis, rabies)
COMMUNICABLE DISEASE
CHANNELS OF
TRANSMISSION OF
INFECTION:
COMMUNICABLE DISEASE
CHANNELS OF
TRANSMISSION OF
INFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNE



Droplet infection
(direct spread):
CSM, Whooping cough
Droplet nuclei
(direct air-borne):
Measles, Chickenpox
Infected dust
(indirect air-borne):
TB, Diphtheria
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNE
Inhalation Infections:
 Respiratory Tract:
•
•
•
•
Pulmonary Tuberculosis.
Influenza
Sore-throat
Pneumonia
•
Common cold
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNE
Inhalation Infections:
 Other Specific Fevers :
•
•
•
•
•
•
•
•
•
Measles.
Whooping cough
Diphtheria
Scarlet fever
Chicken pox
Mumps
Rubella
Cerebrospinal fever
(Small Pox)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNE
Categories:
 The enteric group (salmonellae)
 The dysentery group (shigellae)
 The rotaviruses (G.E.)

Hep A

Cholera

Food poisoning (staph).

Amoebic dysentery.

Helminths.
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNE
Methods of transmission:
 The human hand
 Flies
Musca domestica
House fly
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNE
Methods of transmission:
 Milk: Excellent medium
• T.B.
• F.P.
• Diphtheria
Dirty udder
Dirty hands of milking man
Dirty bottle
 Water:
Very serious
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNE
Methods of transmission:
 Meat:
• Diseased animal
• Contaminated meat.
 Fresh Vegetables and Fruits :
• Poor medium.
• Can be contaminated by:
 Flies
 Washing water
 Dirty hands
 Manure
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
Can be:
 Biological transmission
 Harborage transmission
 Transovarial transmission
 Mechanical transmission
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
Vector:
 Inoculation
 Contamination
skin or
mucous membranes
• By infectious feces.
• Body fluids (when crushed)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
Flies:
• Enteric fevers.
• Mucopurulent conjunctivitis.
• Ascariasis.
• Food poisoning.
• Amoebic dysentery.
• Poliomyelitis.
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
The louse (Pediculum humanus):
• Epidemic typhus.
• L.B. relapsing fever.
human body louse
Human
Head
louse
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
The Flea (Xenopsylla cheopis;
rat flea) :
Bubonic plague
Endemic typhus
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
The Mosquito (female of):
- Culex sp. (filariasis)
- Anopheles sp. (malaria)
- Aedes sp. (yellow fever)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNE
Methods of transmission:
The Sand Fly:
- Cutaneous
Leishmaniasis.
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACT
Methods of transmission:
Can be:
• Direct
• Indirect
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACT
Types:
STD
•
•
•
•
•
?
Syphilis
Herpes simplex
Lymphogranuloma
(AIDS)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACT
Types:
Fungal Infection of the skin
- Tinea capitis (ring worm).
Tinea pedis (athlete’s foot).
- Tinea cruris.
(crotch itch)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACT
Types:
Mycosis
- Moniliasis
(Oral Thrush)
- Mycetoma
Madura foot
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACT
Types:
Scabies:
mite (Sarcoptes scabiei)
Trachoma and other
eye infections.
COMMUNICABLE DISEASE
HOST-PARASITE
RELATIONSHIP
Epidemiologic Triangle
Agent
(Seed)
Environment
(Climate)
Host
(Soil)
COMMUNICABLE DISEASE
HOST-PARASITE
RELATIONSHIP
Infectious Disease Model
Pathogen
Host
disease
Environment
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Disease Agents
•
•
•
•
•
Biological
Physical
Chemical
Mechanical
Nutrient
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Biological Disease Agents
• Bacteria
• Viruses
• Parasites
• Protozoa
• Metazoa
• Rickettsiae
• Fungi
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Microbes-humans Relationship
Very few microbes are
always pathogenic
Many microbes are
potentially pathogenic
Most microbes are
never pathogenic
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Microbes-humans Relationship
(Symbiosis)

Mutualism
- Association in which both partners benefit
(Bacteria and synthesis of vitamins K and B)

Commensalism
- Association in which one partner benefits and
other is unharmed (Flora living on skin)
Parasitism
- Association in which the microbe befits at
expense of host (pathogenic infection)

COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Agent Factors
Intrinsic Properties of “Agent”
- Antigenic make-up.
- Growth requirements.
- Ability to survive outside the host
(milk, water, soil).
- Viability under varying conditions
(temp, humidity).
- Spectrum of hosts.
- Resistance to treatment.
- New genetic information.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Agent Factors
Properties subject to interaction
 Infectivity
 Pathogenicity
 Virulence
 Immunogenicity
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Agent Factors
Properties subject to interaction




Infectivity
Pathogenicity
Virulence
Immunogenicity




Dose
Source
Route
Duration before
reaching the host
 Host characteristics
• Age
• Race
• Nutritional Status
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Host Factors
( a HOST is a PERSON who can be
infected under normal conditions.)
•
•
•
Exposure
Susceptibility
Response to the agent
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Host Factors
Exposure
•
Age
•
Sex
•
Race
•
S.E.S ( occupation)
•
Behavior
•
Drug abuse
•
Sexual practice
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Host Factors
Susceptibility and Response to the Agent
•
Age
•
Pregnancy
•
Malnutrition
•
Immunity
•
Other diseases
•
Medications
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Environmental Factors
1- Physical Environment
• Climate
• Geography
• Water
• Housing
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Environmental Factors
2- Biological Environment
•Man
•Microbes
•Insects
•Rodents
•Animals
• Agents
• Reservoirs
• Intermediate hosts
• Vectors
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Environmental Factors
3- Psychosocial Environment
•
•
•
•
•
Education
Occupation
Beliefs
Attitude
Behavior
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Reservoir of Infection
Types :
1. Human to Human
Human
Human
•
•
•
•
Most viral and bact. RTIs
Most staph and strept.
Childhood exanthemata
STD
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Reservoir of Infection
Types :
2. Animal to Human
Zoonosis
animal
animal
human
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Reservoir of Infection
Types :
3. Complex cycles
- Malaria
- Bilharzia
- Tape worm
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
The Incubation Period :
Initial infection ( exposure )
Onset of clinical disease
( symptoms or signs)
Symptom = subjective complaint e.g.:
pain, loss of appetite, lethargy
Sign = observable or measurable change
in body function eg : rash, fever
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
The Latent Period :
Initial infection
Start of infectiousness
The Period of Communicability:
1. before onset
early in disease course
2. before onset
after recovery
- convalescence
- chronic
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Phases of Disease Cycle:
Incubation period:
-Variable length
-Prior to signs and symptoms
Prodromal stage:
- The period of early symptoms
- Indicates the start of disease before
specific symptoms and signs occur.
- Often infectious/contagious
- Innate immune response starts
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Phases of Disease Cycle:
Illness stage :
- Most severe phase
- Clear evidence of signs and symptoms
- Acquired immune responses begin
Decline stage:
- Alleviation of signs and symptoms
- Recovery/convalescence
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Cycle of Infection
INFECTIOUS AGENT
SUSCEPTIBLE HOST
NEONATES
DIABETICS
IMMUNOSUPPRESSED
CARDIOPULMONARY DISEASE
BACTERIA
VIRUSES
FUNGI
PROTOZOA
HELMINTH
PORTAL OF ENTRY
BROKEN SKIN
MUCOUS MEMBRANES
GIT/RESPIRATORY
URINARY TRACT
RESERVOIR
PEOPLE
EQUIPMENT
WATER
PORTAL OF EXIT
MODE OF TRANSMISSION
AIRBOURNE
INGESTION
INNOCULATION
CONTACT
EXCRETIONS
SECRETIONS
DROPLETS
SKIN
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Outcome of Infection
P
H
R
COLONIZATION A
O
COVERT S
disease
I
S
OVERT T
disease
T
E
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Outcome of Infection
Disease Mechanism
– Tissue invasion
– Toxin production
– Hypersensitivity
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of Infection
Phases of Infectious Disease :
Outcome of Infection
Disease Mechanism
Spectrum of Disease
TB, Polio, Hep A
f
f
f
f
f
Measles, Chickenpox
f
f
f
f
f
Rabies, Amebic Encephalitis, Hemorrhagic Fever.
f f f
f
f
Inapparent
f
f
Mild
f
Moderate
f
Sever
f
Fatal
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Sporadic Disease :
Occurs irregularly and only
occasionally in a population .
e.g. Typhoid fever (Salmonella typhi)
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Endemic Disease :
Constant presence of an infectious
disease within a given geographical
area or population group.
the usual
or
expected
frequency of disease
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Hyperendemic Disease :
When occurrence frequency
rises,
but not to epidemic proportions.
e.g. - Common cold in the winter months
- high prevalence malaria
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Epidemic :
The occurrence of cases of disease,
(( specific health related behavior, or other health related events ))
clearly more than expected
In a given area
or among a specific group of people
over a particular time.
? One example
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Outbreak :
epidemic-like
increase in frequency,
but in a very limited (focal)
segment of the population;
Usually of shorter duration.
Example: Food poisoning,
URTI
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Pandemic :
An epidemic occurring over
a very wide area
(several countries or continents)
and usually affecting a large proportion
of the population
? One example
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Number of Cases of a Disease
Endemic
Epidemic :
Endemic
Time
Epidemic
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Endemic
Epidemic :
Host Factors:
- Change in behavior ?
- Population movement
-
Immunity
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Endemic
Epidemic :
Environmental Factors:
- Adverse conditions:
- War
- Famine
-
Vector:
- Mosquitos
- Flies
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Some Concepts of
Communicable Disease :
Levels of Communicable Diseases Occurrence
Endemic
Epidemic :
Environmental Factors:
- New or
Exposure
- Change in climate
- Irrigation scheme
(- Energy plants)
-
Control measures
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
Can be classified into:
I Controlling the source of infection
II Blocking the channels of transmission
III Protecting the susceptible population
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
I Controlling the source of infection :
(CASES, CARRIERS AND ANIMAL RESERVOIR)
-
Early diagnosis
Notification
Isolation
Treatment
Quarantine
Surveillance
Disinfection
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Air- borne:
- Bed-spacing
- Dust-control
- Effective ventilation
- Good health habits
- Air disinfection
- Use of masks
- Minimize over-crowding
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Food and Drink - borne:
–
–
–
–
–
–
–
–
–
–
Provision of safe/sufficient water.
Pasteurization or boiling of milk.
Proper personal hygiene.
Sanitary sewage disposal.
Control of flies.
Washing fresh vegetables.
Meat and slaughter house control.
Refrigeration of unused food.
Control of food handlers and vendors.
Labs for food examination.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Food and Drink - borne:
FOOD
DRINK
BOTH FOOD
and DRINK
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Arthropod - borne:
Lice:
• Personal cleanliness.
• Avoiding overcrowding.
• Dusting by insecticides.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Arthropod - borne:
Fleas:
• Cleanliness of dwellings.
• Avoid dust collection.
• Spraying & dusting by
insecticides.
• Rodent control.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Arthropod - borne:
Mosquitos :
• Vector control.
• Personal protection.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Contact Diseases :
-
Case finding and treatment.
Tracing of contacts.
Serological examination.
Control of sexual behaviour.
Personal cleanliness.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
II Blocking the channels of transmission :
Contact Diseases :
- Avoid use of common articles:
- Comb.
- Hair brush.
- Towels.
- Handkerchief.
- Underwear.
- Footwear ……. etc.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Primary Prevention:
- Health promotion.
- Specific protection.
- Secondary Prevention:
- Early diagnosis and
- Prompt treatment.
- Tertiary Prevention:
- Limitation of disability.
- Rehabilitation.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Primary Prevention:
- Health promotion.
- Adequate nutrition.
- Health education.
- Socio-economic development.
- Environmental sanitation.
- Personal hygiene.
(- Genetic counseling.)
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Primary Prevention:
- Specific protection.
- Specific immunization.
-- Protection
Protectionagainst
againstoccupational
occupationalhazards.
hazards.
-- Protection
Protectionagainst
againstaccidents.
accidents.
-- Protection
Protectionfrom
fromcarcinogens.
carcinogens.
-- Avoidance
Avoidanceof
of allergens.
allergens.
allergens.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Secondary Prevention:
- Early diagnosis and
- Prompt treatment.
- Health education
- Screening for
sub-clinical disease.
- Case finding
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Tertiary Prevention:
- Limitation of disability.
- Adequate treatment.
- Rehabilitation.
- Psychological:
- Restoration of personal
confidence and independence.
- Medical:
- Physical restoration of function.
COMMUNICABLE DISEASE
HOST-PARASITE RELATIONSHIP
Control of
Communicable Disease :
III Protecting the susceptible population :
- Tertiary Prevention:
- Rehabilitation.
- Vocational:
- Restoration of capacity to
earn. (Occupational)
- Social:
- Restoration of family and
community relationship.
COMMUNICABLE DISEASE
Natural History of Disease
Recovery
COMMUNICABLE DISEASE
Natural History of Disease
Recovery
COMMUNICABLE DISEASE
Natural History of Disease
Recovery
COMMUNICABLE DISEASE
Natural History of Disease
Recovery
COMMUNICABLE DISEASE
Natural History of Disease
Recovery