Nursing College – Mosul UniversityEntry of pathogens:
The extent of the spread of an infection agent
in the body and length of time between
exposures to the agent on onset of disease
symptoms which called "Incubation period. e.g.
typhoid fever disease many as 10.000 peoples
that exposure in 1963 in Switzerland by drinking
water contaminated with Sal. typhi the cause of
the disease the long I.P. of the disease 10 - 14
days allowed widespread .
Respiratory tract system :e .g . mumps , measles , Streptococcus , etc .
Digestive tract :
such as Clostridium perfringens (welchii ), Salmonella
typhi , Strep . Spp .
Urinary Tract :e .g . E .coli , Klebssiella , Proteus .
Genital tract :e .g . Gonococcus infection by N gonorrhea ,
Trichomonasis disease by Trichomonas vaginlis or
Syphilis cause by Treponema palladium .
Through skin :. E .g . Gas gangrene cause by Clostridium
welchii or . Cl . tetani , Staph . Aurous, Smallpox virus, and
Herpes virus .
The route of any infectious agent:
Communicable disease:• Communicable disease are infectious
disease when the source of infection
is human (man) e.g. measles, mumps,
hepatitis, AIDS, but sometimes not
human e.g. brucellosis,
• Period of communicability is the
time of transfer of pathogenic
microorganism to form disease .
Types of communicable disease :• Pathogenic microorganisms transmitted through
mucous membrane stick on it and causing fever
e .g . Diphtheria, measles, mumps .
• Late incubation period - clinical course -
convalescent - post convalescent period . (few
days - several weeks) e .g . poliomyelitis,
• Disease transmitted by sucking of arthropod
period (the period when the microorganism
found in blood) e .g . malaria, Leshmania, typhus
fever, yellow fever .
Communicable disease occur in every country,every urban and rural area, and in every
neighborhood from the very rich to the very
poor . Nurses who provide care in combating
communicable disease must have a basic
understanding of epidemiology infection
control, microbiology, medicine, public health
and nursing . Furthermore the community nurse
must be having knowledge of the legal system
which mandates prevention and control of
communicable disease locally, nationally, and
Applied of epidemiologic Principlesand Methods :
Epidemiology began as the study of
communicable disease affecting large
population . Although the scope of
epidemiology has expanded to include
noncommunicable disease and other
health - related issues, epidemiologic
principles are still the backbone of
communicable disease control .
Preventing communicable disease beginswith knowledge about :
▪ The links in the chain of infection.
▪ The relationships and interactions among -
- The infectious agent (causative
- The host (human or animal incubating the
- The environment (i.e., the epidemiology
Communicable disease control dependson :
1. Discovering the weak link in the triangle.
2. Developing measures that attack and
reduce or eliminate that threat.
3. Control efforts include prevention
activities and efforts to reduce the
seriousness of an illness as measured by
severity, the length of illness , the cost of
treatments , the short - and long - term
effects, and the risk of death
Communicable Disease Investigation:In accordance with epidemiologic
principles, communicable disease
investigation involves five steps:
1 - Identify the disease.
2 - Isolated the causative agent.
3 - Determine the method of transmission.
4 - Establish the susceptibility of the
population at risk.
5 - Estimate the impact on the population.
Causative agent : Pathogenicity, invasiveness, virulenceand active inactive dose .
Means of transmission : Direct or indirect contact,
source to a new host or carrier droplets etc .
Characteristic of host : Immunity defense mechanisms
include tears, skin, mucus, saliva and cilia – hairs in nose ,
also as natural or artificial immunity , active or passive
Environment : Communicable disease control as
temperature, humidity radiation, pressure, and ventilation
.By this can all be used to decrease the transmission of
infectious disease . Crowding, famine, and mobility of
people increase the possibility of spreading disease .
Fig. 2.2 transmission 0f communicable diseaseFig: 2.3 breaking the chain of infection in HIV and AIDS.
Chickenpox Vercella - ZosterVirus (VZV)
14 -16 days
2 -5 days
Pertusis Bordetella pertusis 6 -20 days
Rubella virus, Rubivirus
Measles/rubella Rubeda virus 9 -12 days
Mumps Mumps virus 16 -18 days
1: Respiratory Route :
Disease Causative agent Incubation peioroid
Mumps Mumps virus 16 -18 daysTuberculosis (TB) Myco.
(d) several weeks
Inf luenza virus , (f lu) 1-2 days
Mononucleosis Epstein - Barr
Kissing disease (EPU)
Inf luenza Hemophilus
less than 10 days
Erthema infectious Illness rash Week -months
Scarlet fever B - hemolytic
Impetigo Group AStreptococcus or
4 -10 days
Pediculosis Parasitic lice Lice 10 days
Scabies Parasitic mite Long as eggs or
mites are alive
Tetanus Clostridium tetani Ally 8 days
2: IntegumentaryRoute :
Poliomyelitis Poliovirus 6 -20 daysSalmonellosis Salmonella typhior
7 -10 days
Shigella spp. (week) depend
Intestinal parasites (round worms and
Months or more
Toxoplasmosis Toxoplasma gondii Long periodic
(protozoa) Latent phase
Hepatitis A ( HAV ) Hepatitis A virus 15 -40 days
3: Gastrointestinal Route :
Hepatitis B (HBV )
Hepatitis B virus
1 - 6 months
2 - 10 years
4 : Serum Route :
5: Sexually Transmitted Route :Herpes Herpes simplex
virus(HSV -1) (HSV -2)
2 -12 days After
(CMV) 6 months
Venereal warts or HPV Papiloma virus 1 -3 months
Gonorrhea Neisseria gonorrhea 2 days -3 weeks
Chlamydia Chlamydia spp. 5 days - longer
Syphilis Treponemapallidum 3 -6 weeks
Disease:Disease is Latin word mean dis = lack, ease = power mean
lack of power or discomfort . Disease defines as abnormal
state in which body physiology can't restore body comfort.
Any disease results from end of two forces:
Force of agent depend on :
Type of agent.
Virulence factor of agent
Dose of infected agent .
Force of host depend on :
Acquired immunity .
Force of host Force of agent End resultsVery high Very low No disease
High Low Subclinical
Mild Mild Sign and symptom
Low High Moderate or
Very low Very high Fulminate (very
Low Rapid Exotoxins large death
Disease InvestigationEstablish diagnosis
Identify specific agent
Describe according to person, place
Identify source of agent
Identify mode of transmission
Identify susceptible populations
End result of the disease :1. Complete recovery.
2. Clinical case (carrier).
3. Recovery with defect.
Incubation period start from the entrance
of micro - organisms to the body until the
appearance of sign a symptoms, (clinical
cores of disease the appearance of sign