Download Communicable Disease Control

Communicable Disease Control
Soili Larkin & Joshna Mavji
Aim
To understand key principles for
communicable disease control
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Communicable Disease Control
Objectives
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Define communicable diseases
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Describe modes of transmission of communicable diseases
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Describes measures of infection prevention
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List key notifiable diseases
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Outline the role of PHE Health Protection Teams in communicable disease
control
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Describe the process of responding to a case of communicable disease
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Demonstrate awareness of key communicable diseases (Meningococcal
disease, E. coli, Tuberculosis, Ebola)
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Communicable Disease Control
What are Communicable Diseases?
Communicable diseases spread from one person to another or from an animal
to a person. The spread often happens via airborne viruses or bacteria, but
also through blood or other bodily fluid. The terms infectious and contagious
are also used to describe communicable disease.
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Communicable Disease Control
Communicable Disease Control: Modes of
Transmission
Contact
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Direct
Direct physical contact (body surface to body surface) between infected
individual and susceptible host.
Examples: Influenza virus; Infectious mononucleosis; chlamydia.
Precautions: Hand hygiene; masks; condoms.
Indirect
Infectious agent deposited onto an object or surface and survives long
enough to transfer to another person who subsequently touches the object.
Examples: RSV; norovirus; rhinovirus.
Precautions: Sterilising instruments; disinfecting surfaces and toys in school.
Droplet
Via coughing or sneezing, or (in health care) during suctioning. Droplets are
relatively large (>5 µm) and can be projected up to about one metre.
Examples: Meningococcus; pertussis; scarlet fever
Precautions: Masks; isolating case.
Communicable Disease Control
Communicable Disease Control: Modes of
Transmission
Noncontact
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Airborne Transmission via aerosols (airborne particles <5µm) that contain organisms
in droplet nuclei or in dusts. Examples: TB; measles; chickenpox;
Precautions: Masks; negative pressure rooms in hospitals.
Vehicle
A single contaminated source spreads the infection (or poison). This can be
a common source or a point source.
Examples
a) Point source: Food-borne outbreak from infected batch of food;
b) Common source: A Listeriosis outbreak in Canada was linked to a meat
production facility. It caused 20 cases across nationally. Cases may be
widely dispersed due to transport and distribution of the vehicle.
Precautions: Normal safety and disinfection standards.
Vectorborne
Transmission by insect or animal vectors.
Example: Mosquitoes –malaria vector, ticks –Lyme disease vector.
Precautions: Protective barriers (window screens, bed nets); insect sprays;
culling animals.
Communicable Disease Control
Standard Infection Prevention Precautions
Hand Hygiene
Single most important part of infection
control
Hand washing before any contact with
patients, after any activity that
contaminates the hands, after removing
protective clothing, after using the toilet
and before handling food
Decontaminating equipment: cleaning,
disinfection and sterilization
Preventing occupational exposure to
infection
Managing sharps injuries and blood splash
incidents appropriately
Isolation / Quarantine
Use of personal protective equipment (PPE):
gloves, aprons, eye protection, face
masks etc.
Correct disposal of excretions & soiled
material
Handling and disposing of sharps safely
Disinfection, especially important in
nurseries, schools & residential
institutions
Disposing of contaminated waste safely
Managing blood and body fluids: spillages
and transport of specimens
Education
Routine and selective immunisation
Screening
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Communicable Disease Control
Notifiable Diseases (NOIDs)
Acute encephalitis
Infectious bloody diarrhoea
Scarlet fever
Acute infectious hepatitis
Invasive group A streptococcal
disease
Smallpox
Acute meningitis
Acute poliomyelitis
Anthrax
Botulism
Brucellosis
Cholera
Diphtheria
Enteric fever (typhoid or
paratyphoid fever)
Legionnaires’ disease
Leprosy
Malaria
Measles
Meningococcal septicaemia
Mumps
Plague
Rabies
Food poisoning
Rubella
Haemolytic Uraemic Syndrome
Severe Acute Respiratory
Syndrome (SARS)
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Communicable Disease Control
Tetanus
Tuberculosis
Typhus
Viral haemorrhagic fever (VHF)
Whooping cough
Yellow fever
Other significant disease
(diseases that may present
significant risk to human
health)
Communicable Disease Control: Role of
PHE Health Protection Teams
• Protect the population from infection and environmental hazards
through a range of core functions including:
 Surveillance and analysis of trends in communicable disease
 Operational support and advice to those involved in the prevention,
investigation and control of infectious diseases and environmental
hazards
 Education & training e.g. outbreak exercises
 Research
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Communicable Disease Control
Communicable Disease Control:
Responding to a Case
What investigations (microbiological / environmental / epidemiological) are needed to identify the
agent, the cause of the incident?
What is the source of infection?
• Is it a continuing source that may need to be controlled? If so, what generic control measures can be
applied to limit morbidity whilst awaiting confirmation e.g. enhanced hand washing, environmental
cleaning etc.
• Are there others exposed who may need advice / treatment?
What is the likelihood of transmission?
• Advice / prophylaxis to close contacts e.g. hepatitis B immunisation
• Occupational transmission e.g. exclusion of food handlers with gastrointestinal infection
Is public health action necessary?
• How infectious is the source? - Is the index case at risk of a poor outcome?
• Is the index case likely to pass the infection to others? - How close is the contact?
• Do contacts and others exposed to the same source need to be traced?
• How susceptible are those exposed?
• Is there likely to be an ongoing source that needs controlling?
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Communicable Disease Control
Communicable Disease Control:
Responding to a Case
Does public health action need to be done
immediately?
Determined by:
Possible interventions
• Treatment of case
• Prophylaxis
• Seriousness of disease
• Isolation
• Transmissibility of infection
• Hygiene advice
• Length of incubation period
• Exclusion
• Vulnerability of people exposed
• Closure of premises associated with incident
• Public/ media / political reaction
• Evidence based practice
Communication
• Cases / contacts / clinicians
• Internal - specialist advice within PHE /
microbiology
• External - local authorities, press e.g. outbreak
of meningococcal disease in a school
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Communicable Disease Control
Examples of Key Infections – Meningococcal disease
Causal agent
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Meningococcal meningitis and meningococcal septicaemia are systemic infections
caused by the bacteria Neisseria meningitidis.
Clinical features
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The infection may present as meningitis, septicaemia or a combination of both1.
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Sudden onset of fever, malaise, increasing headache, nausea, vomiting,
photophobia, neck stiffness, non-blanching rash
Communicable Disease Control
Examples of Key Infections – Meningococcal disease
Reservoir
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Humans
Mode of transmission
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Person to person, transmitted by droplet aerosol or secretions from the
nasopharynx of colonised individuals
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Transmission requires either frequent or prolonged close contract
Incubation period
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2-10 days
Period of communicability
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While live meningococci are present in discharges from nose and mouth.
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Meningococci usually disappear from the nasopharynx within 24 hours of
appropriate antibiotic treatment.
Communicable Disease Control
Examples of Key Infections – Meningococcal disease
Epidemiology
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The majority of meningococcal infections occur in children under 5 years, with a
peak incidence at 6 months of age. There is a smaller, secondary peak in
incidence among young adults aged between 15-19 years of age.
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Marked seasonal variation with the highest incidence occurring in winter
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Most cases of meningococcal disease occur sporadically, with <5% of cases
occurring in clusters.
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Outbreaks are more common among teenagers and young adults in schools and
university
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Since the introduction of Men C vaccine into the UK routine immunisation
programme the number of laboratory confirmed group C cases have fallen by over
90% among all age groups immunised. Cases among other age groups have fallen
as a result of reduced carriage rates.
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In the UK, serogroup B is now responsible for >85% of laboratory confirmed cases
Communicable Disease Control
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Number of Cases
Seasonal Trends in Meningococcal Disease
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Communicable Disease Control
2011
Year of Onset
Confirmed Cases
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Three Week Rolling Average
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Examples of Key Infections – Meningococcal disease
Public health management
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Indicated for confirmed or suspected cases
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Trace close contacts: close household contacts (those with an overnight stay
and/or +8hrs of continuous contact), intimate contacts
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Antibiotic prophylaxis for close contacts - to eradicate nose and throat carriage
(thus limiting further spread) and to eradicate carriage from those who may have
recently acquired an invasive strain
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Casual contacts such as those in a same school, nursery, party etc. are not usually
offered prophylaxis
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If the strain is found to vaccine-preventable, contacts are offered vaccination within
4 weeks of the case occurring
Communicable Disease Control
Examples of Key Infections – E. coli
Causal agent
• Many different strains of Escherichia coli can cause diarrhoeal illness
• The most serious is verocytotoxic E.coli (VTEC) which can cause
haemolytic uraemic syndrome (HUS) which can lead to renal failure and
death.
Clinical features
• Diarrhoea (often bloody)
• Abdominal cramps / pain
• HUS is characterised by acute renal failure,
haemolytic anaemia and thrombocytopaenia
(lowered platelets).
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Communicable Disease Control
Examples of Key Infections – E. coli
Epidemiology
• Highest incidence rates in the UK occur in children < 5 years
• Summer peak
Reservoir
• Gastrointestinal tract of animals – mainly cattle
Mode of transmission
• Consumption of contaminated, undercooked or raw foods, mainly beef
• Consumption of unpasteurised milk
• Cross contamination during food preparation
• Person to person via faeco-oral route
• Direct contact with animals e.g. school visits to farms
• Waterborne transmission occurs through swimming in or consuming
contaminated water.
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Communicable Disease Control
Examples of Key Infections – E. coli
Incubation period
• 2-10 days, median 3-4 days
Period of communicability
• Up to 1 week in adults, while excreting the pathogen
• Up to 3 weeks in children, while excreting the pathogen
Public health management
• Minimisation of contamination at slaughter
• Good kitchen hygiene and food preparation practices
• Pasteurisation
• Effective hand hygiene
• Infection prevention precautions during farm visits
• Protection of drinking water supplies
• Good hygiene practices for swimming
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Communicable Disease Control
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Confirmed VTEC O157 Cases by Month in the West
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Communicable Disease Control
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Examples of Key Infections – Tuberculosis (TB)
Causal agent
• Mycobacterium tuberculosis
Clinical features
• Persistent cough lasting 3 weeks or more that may produce discoloured
or bloody sputum.
• Pain with breathing or coughing (pleurisy)
• Weight loss
• Symptoms of TB disease in other parts of the body depend on the area
affected.
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Communicable Disease Control
Examples of Key Infections – Tuberculosis (TB)
Reservoir
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Primarily humans
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In some areas diseased cattle, badgers, swine and other mammals are infected
Mode of transmission
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Person to person via inhalation of M. tuberculosis bacilli in droplet nuclei from
coughing, sneezing and talking (requires close and prolonged contact)
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Bovine TB is spread primarily through the ingestion of unpasteurised milk or milk
products and in some cases through airborne transmission.
Incubation period
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3-12 weeks (from infection to reaction to tuberculin test).
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Latent infection may be many decades
Communicable Disease Control
Examples of Key Infections – Tuberculosis (TB)
Epidemiology
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In 1993 the World Health Organization declared TB a 'global emergency'.
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TB remains one of the world's leading infectious causes of death among adults.
1/3rd of the world's population is infected with the TB bacillus.
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Leading cause of death among people who are HIV-positive.
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Risk factors: Family/household contacts of cases diagnosed with TB (identified
through contact-tracing), homelessness, history of alcohol/drug misuse, immigrants
from high TB prevalence areas, individuals who frequently spend long periods of
time in high TB prevalence areas, immunosuppression.
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In the UK 2/3rds of TB disease is pulmonary which is the infectious form of TB.
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10% of those initially infected will eventually develop active TB disease. 90% of
untreated infected individuals will never develop active TB (latent TB infection).
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Bacilli survive in latent form which may reactivate in later life. The risk of
reactivation increases with age, chronic disease and immunosuppression.
Communicable Disease Control
Examples of Key Infections – Tuberculosis (TB)
Period of communicability
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Most sputum smear positive cases stop being infectious after 2 weeks following
appropriate treatment
Public health management
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Tuberculosis is a statutorily notifiable disease
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In England and Wales enhanced TB surveillance started in January 1999.
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In September 2005, a targeted BCG vaccination programme came into effect for:
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All infants living in areas where the incidence of TB is ≥40/100,000 population
All infants with a parent or grandparent who was born in a country where the
incidence of TB is >40/100,000 population.
TB infection can be cured with appropriate antibiotic treatment.
Communicable Disease Control
Estimated TB incidence Rates, 2013
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Communicable Disease Control
Tuberculosis in the UK, 2013
Source: TB in the UK: 2014 Report
https://www.gov.uk/government/publications/tuberculo
sis-tb-in-the-uk
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Communicable Disease Control
Tuberculosis in West Midlands
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Communicable Disease Control
Examples of Key Infections – Ebola Virus Disease
One type of viral haemorrhagic fever
Causal agent
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Ebola virus
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A zoonotic virus
Clinical features
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Initial: Fever, chills, aches and pains, malaise, lack of appetite
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After 5 days: nausea, vomiting, watery diarrhea, abdominal pain
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Additional symptoms: headache, conjunctivitis, hiccups, rash, chest pain,
shortness of breath, confusion, seizures
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Other possible infectious causes of symptoms: Malaria, typhoid fever, meningitis
and other bacterial infections (e.g pneumonia) – all very common in Africa
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Non-fatal cases typically improve 6–11 days after symptoms onset
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Fatal disease associated with severe early symptoms. Case fatality rate – 50-90%
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Intensive care, especially early intravenous fluids, may increase the survival rate
Communicable Disease Control
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Communicable
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Source: en.wikipedia.org
Examples of Key Infections – Ebola Virus Disease
Epidemiology
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Ebola was first identified in 1976 in Sudan and the Democratic Republic of Congo
following large outbreaks.
Reservoir
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Unknown – Primates and bats considered to be most likely reservoir
Mode of transmission
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Spillover event from infected wild animals (e.g., fruit bats, monkey etc.) to humans,
followed by human to human transmission
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Person to person via contact with bodily secretions, organs and blood of infected
individuals.
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The handling of infected primates
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Direct contact with the body of a deceased person infected with the virus.
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Nosocomial transmission occurs frequently during outbreaks.
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Sexual transmission following recovery from infection – virus isolated from semen
upto three months after initial infection
Communicable Disease Control
Examples of Key Infections – Ebola Virus Disease
Incubation period
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2-21 days.
Period of communicability
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During acute illness
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Infectiousness of body fluids (e.g. viral load) increases as patient becomes more ill
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Remains from deceased infected persons are highly infectious
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There is no carrier state.
Public health management
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No effective treatment is available.
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Severe cases require intensive supportive care.
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There is no vaccine against ebola haemorrhagic fever.
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Strict isolation of cases and strict barrier nursing techniques implemented.
Communicable Disease Control
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Communicable Disease Control
Sourcehttp://www.abc.net.au/news/201410-09/how-infectious-is-ebola/5802524
Outbreaks of Ebola – How do they start?
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Most outbreaks in remote areas
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Initially diagnosed as a different febrile illness e.g. Malaria, Typhoid etc.
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Patient cared for by relatives before they get to hospital or throughout entire
illness (if they live in a remote area) so relatives become infected
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Health care workers become infected because disease not recognised and
precautions not implemented
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Grieving and burial processes of infected individual e.g. holding and
washing
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Communicable Disease Control
Outbreaks of Ebola – Current Outbreak
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Began in Guinea in 2013 and spread
mainly to Liberia and Sierra Leone
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Largest outbreak on record
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First outbreak to affect an urban area
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Overwhelmed existing over-stretched
health services
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Index case believed to be a child who
died in a village in Guinea. Family
members developed similar symptoms
and subsequently died. As no cases had
ever been reported in West Africa, these
cases were diagnosed with other
diseases more common to the area,
therefore it took several months before it
was recognised as Ebola.
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Communicable Disease Control
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Communicable diseases