Download Communicable disease 2017

COMMUNICABLE DISEASE
Week 6
Nur631 Public Health Nursing and Epidemiology
objectives
• review the chain of transmission in infectious/ communicable
disease.
• discuss the causation of emerging and re-emerging infectious /
communicable disease.
• describe the role and function of the nurse in the control of
communicable disease.
• knowledge and use of the reporting system for notifiable
diseases.
• explain the ethic –legal issues that the nurse will encounter
when caring for client’s suffering from and infectious/
communicable disease.
epidemiologic triad
The Triangle has three corners (called vertices):
• Agent, or microbe that causes the disease (the “what” of the
Triangle)
• Host, or organism harbouring the disease (the “who” of the
Triangle)
• Environment, or those external factors that cause or allow
disease transmission (the "where” of the Triangle)
epidemiologic triad
The mission of an epidemiologist is to break at least one of the
side of the Triangle.
The Agent—“What”
• The agent is the cause of the disease.
• Disease-causing microbes are bacteria, virus, fungi, and protozo
a (a type of parasite). They are what most people call “germs.”
The Host—“Who”
• Hosts are organisms, usually humans or animals, which are
exposed to and harbor a disease.
• The host can be the organism that gets sick, as well as any animal
carrier (including insects and worms) that may or may not get sick.
• Different people may have different reactions to the same agent
The Environment—“Where”
• The environment is the favourable surroundings and conditions
external to the host that cause or allow the disease to be
transmitted.
Characteristics of infectious disease agents
• Pathogenicity: refers to the capacity of the agent to cause disease
in infected host.
• Virulence: refers to the severity of the disease.(i.e. , whether sever
e clinical manifestations are produced.
• e.g. The Rabies virus, which almost always produces fatal disease
in humans.
• Resistance: refers to the ability of the agent to survive adverse env
ironmental conditions.
• Infectivity: refers to the capacity of the agent to enter and
multiply in a susceptible host and thus produce infection or
disease.
• e.g. Polio and measles are diseases of high infectivity.
Chain of Infection
• Disease transmission occurs when the agent leaves its
reservoir or host through a portal of exit, is
conveyed by some mode of transmission, and enters
through an appropriate portal of entry to infect a
susceptible host.
Chain of Infection
Reservoir
• The reservoir of an infectious agent is the habitat in wh
ich the agent normally lives, grows, and multiplies.
• Reservoirs include humans, animals, and the
environment.
• Microorganisms can thrive in human beings, animals
and inanimate objects such as water, table tops and
door knobs.
Reservoir
Human reservoirs
e.g. sexually transmitted diseases, measles, mumps,
streptococcal infection, and many respiratory pathogens
• Carrier is a person with inapparent infection who is
capable of transmitting the pathogen to others.
• Incubatory carriers are those who can transmit the
agent during the incubation period before clinical illne
ss begins
Reservoir
• Convalescent carriers are those who have recovered
from their illness but remain capable of transmitting
to others.
• Chronic carriers are those who continue to harbor a
pathogen such as hepatitis B virus or Salmonella Typhi
the causative agent of typhoid fever, for months or
even years after their initial infection.
Portal of exit
• It is a place of exit providing a way for a microorganism
to leave the reservoir.
• Principal portals of exit are: Digestive system, urinary
system, respiratory system, reproductive system and
the blood.
Modes of transmission
Direct:
• Direct and immediate transfer of infectious agents to a
receptive portal of entry through which human or
animal infection may take place.
• e.g. touching, biting, kissing or sexual intercourse, or
by direct droplet spray onto the mucous or
conjunctiva membranes of the eye, nose, or mouth du
ring sneezing, coughing, spitting, singing, or talking
(usually at a distance of 1 meter or less).
Modes of transmission
Indirect:
Vehicle-borne – Vehicle (Transmission)- any mechanism
by which a susceptible host is exposed to an infectious
agent.
Contaminated inanimate materials or objects (fomites)
such as toys, handkerchiefs, soiled clothes, bedding,
cooking or eating utensils, surgical instruments or
dressings; water, food, milk, biological products including
blood
Modes of transmission
Vector-borne: Spread by animals, most often arthropods.
Vector-borne diseases include those spread by ticks and
mosquitoes.
Airborne: Spread through the air. An organism spread in
this way can be suspended in air. It is similar to a droplet
spread organism because an infected person can spread i
t by coughing, sneezing or talking, and an uninfected pers
on can become infected by inhaling the organism
Modes of transmission
Natural History of Disease Timeline
Modes of transmission
Iceberg Concept of Infection
The iceberg concept of infection posits that the tip of
the iceberg, which corresponds to active clinical
disease.
Any Questions?
Vectors
Vectors are transmitters of disease causing organisms known as
pathogens. They carry pathogens from one host to another
Chikungunya
• Chikungunya (also known as ChikV) is a virus infection that
can cause a devastating illness.
• It is transmitted to people by Aedes aegypti and Aedes albopi
ctus mosquitoes, the same mosquitoes that transmit Dengue.
• Aedes aegypti is a household container breeder, an aggressive
daytime biter attracted to humans, and it is the primary vecto
r of the Chikungunya virus.
Chikungunya
Chikungunya Signs and Symptom
Principal symptoms are most often characterized by
•Fever,
•Headache,
•Fatigue,
•Nausea, and vomiting
•Muscle pain,
•Rash
•Joint pain - often in the hands and feet.
There is no vaccine or specific antiviral treatment currently available for
Chikungunya fever, but there are medications that can help reduce the fever
and pain.
Zika Virus
• Zika virus is an emerging disease in the United States.
• It was first identified in 1947 in Uganda.
• The first large outbreak of disease caused by Zika virus infecti
on was reported from the Island of Yap in 2007.
• These mosquitoes are aggressive daytime biters but can also
bite at night.
• Currently, there is no vaccine or medicine for Zika virus, but re
searchers are currently working on efforts to address this.
Zika Virus Transmission
• The transmission of Zika virus to humans can occur in several
different ways.
• The primary route of transmission is through the bite of an
infected mosquito.
• pregnant woman is infected, she can pass Zika virus to her
fetus during pregnancy or around the time of birth.
• Zika virus can also be passed through sex from an infected
person to his or her partners,
• Another probable route of transmission for Zika virus is
through blood transfusions.
Zika Virus
Vectors are transmitters of disease causing organisms known as
pathogens. They carry pathogens from one host to another
Zika Virus
Many people infected with Zika virus will have no symptoms
or will have only mild symptoms.
symptoms of Zika virus, the most common ones include:
• Fever
• Rash
• Joint pain
• Conjunctivitis (red eyes)
• Headache
• Muscle pain
Zika Virus
Emerging infectious disease
• Newly identified & previously unknown infectious agents that
cause public health problems either locally or internationally
Re-emerging infectious disease
• Infectious agents that have been known for some time, had
fallen to such low levels that they were no longer considered
public health problems & are now showing upward trends in
incidence or prevalence worldwide
Factors Contributing To Emergence
• Evolution of pathogenic infectious agents (microbial adaptation
& change)
• Development of resistance to drugs
• Resistance of vectors to pesticides
• Human demographic change (inhabiting new areas)
• Human behavior (sexual & drug use)
• Human susceptibility to infection (Immunosuppression)
• Poverty & social inequality
• Climate & changing ecosystems
• International travel & commerce
• Deterioration in surveillance systems