Repressive anti-epidemic measures;
epidemiological investigation at the outbreak
MUDr. Marie Kolářová,CSc.
Ústav ochrany a podpory zdraví LF MU
Spring 2019
Chain of infections
(epidemic proces)
THE CAUSATIVE AGENT OF INFECTION (bacteria, viruses, fungi, prions, protozoa)
1. the presence of rezervoir (source) of infection
man, animal at the ende of incubation period
acute stage
cariers
2. the way of transmission A/ direct contact
touching, kissing or sexual intercourse (Staphylococcus spp., Gonococcus spp.,HIV …),
- vertical transmission – from mother to fetus (VHB, VHC, HIV, listeria, rubella,
cytomegalovirus…)
B/ indirect contact
- inhalation of droplets containing the infectious agents (TBC, measles, influenza…)
- ingestion of food or water that is contaminated (salmonella, Norwalk virus, VHA….)
- biological transmission by insects (malaria, borellia….)
3. the susceptibility of the population or its individual members to the organism concerned
Host factors : a g e , n u t r i t i o n, g e n e t i c s
i m m u n i t y – natural (nonspecific),
- acquired
THE INFECTION
= 1. source of infection
……….
Chain of infections
(epidemic proces)
If the epidemiology is know, we can interfere with
transmission:
„BREAKING THE CHAIN OF INFECTION“
Different infections have different epidemiologies and thus
require different methods of control
Outbreak
 Sporadics diseases
 An outbreak is a sudden increase in occurrences of a disease in
a particular time and place. It may affect a small and localized
group or impact upon thousands of people across an entire
continent.
 Two linked cases of a rare infectious disease may be sufficient to
constitute an outbreak.
 Outbreaks include epidemics, which term is normally only used
for infectious diseases, as well as diseases with an
environmental origin, such as a water or foodborne disease.
They may affect a region in a country or a group of countries.
 Pandemics are near-global disease outbreaks.
5
Repressive
measures
Solving
health
problem
Step 1
Date collection
Step 2 Assessment
Step 3
Hypothesis testing
Step 4
Action
Surveillance; determine
time, place and person
Inference
Determine how and why
Intervention
Outbreak
investigation
When investigating disease outbreaks, the epidemiology profession has developed a number of widely accepted steps:
 Identify the existence of the outbreak (Is the group of ill persons normal for the time of year, geographic area, etc.?)
 Verify the diagnosis related to the outbreak
Create a case definition to define who/what is included as a case
Case definition, in epidemiology, set of criteria used in making a
decision as to whether an individual has a disease or health event of
interest.
Establishing a case definition is an imperative step in quantifying the
magnitude of disease in a population.
Case definitions are used in ongoing public health surveillance to track
the occurrence and distribution of disease within a given area, as well
as during outbreak investigations in field epidemiology.
Repressive antiepidemic
measures:
isolation,
case definition
Case definitions of communicable diseases:



Case classification –
 Possible,
 Probable,
 Confirmed case.
Clinical criteria
Laboratory criteria
Epidemiological criteria and epidemiological link
Repressive antiepidemic
measures:
isolation,
case definition
Case definitions of communicable diseases:
Clinical criteria include common and relevant signs and symptoms
of the disease which either individually or in combination
constitutes a clear or indicative clinical picture of the disease.
They give the general outline of the disease and do not
necessarily indicate all the features needed for individual clinical
diagnosis.
Clinical criteria
Viral hepatitis A
(VHA)
Case definition
Clinical Criteria
Any person with a discrete onset of symptoms (e.g. fatigue,
abdominal pain, loss of appetite, intermittent nausea and vomiting)
 AND
At least one of the following three:
* — Fever
* — Jaundice
* — Elevated serum aminotransferase levels
Repressive antiepidemic
measures:
isolation,
case definition
Case definitions of communicable diseases:
Laboratory criteria are a list of laboratory methods that are used to
confirm a case.
Usually only one of the listed tests will be enough to confirm the
case. If a combination of methods is needed to meet the
laboratory confirmation, this is specified.
The type of specimen to be collected for the laboratory tests is
only specified when only certain specimen types are considered
relevant for the confirmation of a diagnosis.
Those laboratory criteria consist of a list of laboratory methods
which can be used to support the diagnosis of a case but which
are not confirmatory.
Clinical criteria
Laboratory criteria
Viral hepatitis A
(VHA)
Case definition
Laboratory Criteria
At least one of the following three:
— Detection of hepatitis A virus nucleic acid in serum or stool
— Hepatitis A virus specific antibody response
— Detection of hepatitis A virus antigen in stool
Repressive antiepidemic
measures:
isolation,
case definition
Case definitions of communicable diseases:
Epidemiological criteria are deemed to have been met
when an epidemiological link can be established.
Clinical criteria
Laboratory criteria
Epidemiological criteria and epidemiological link
EU definitions –
case definitions for
reporting
communicable
diseases
Epidemiological link, during the incubation period, means one of the following six:
— 1. Human to human transmission: the fact that a person has had contact with a
laboratory confirmed human case in such a way as to have had the opportunity to
acquire the infection
— 2. Animal to human transmission: the fact that a person has had contact with an
animal with a laboratory confirmed infection/colonisation in such a way as to have
had the opportunity to acquire the infection
— 3. Exposure to a common source: the fact that a person has been exposed to the
same common source or vehicle of infection, as a confirmed human case
— 4. Exposure to contaminated food/drinking water: the fact that a person has
consumed food or drinking water with a laboratory confirmed contamination or has
consumed potentially contaminated products from an animal with a laboratory
confirmed infection/colonisation
— 5. Environmental exposure: the fact that a person has bathed in water or has had
contact with a contaminated environmental source that has been laboratory
confirmed
—6. Laboratory exposure: the fact that a person has worked in a laboratory where
there is a potential for exposure
EU definitions –
case definitions for
reporting
communicable
diseases
Transmission may occur by one or more of the following routes:
— Airborne: by projection of aerosol from an infected person onto the
mucous membranes while coughing, spitting, singing or talking, or when
microbial aerosols dispersed into the atmosphere are inhaled by others
— Contact: direct contact with an infected person (faecal-oral, respiratory
droplets, skin or sexual exposure) or animal (e.g. biting, touching) or
indirect contact to infected materials or objects (infected fomites,
body fluids, blood)
— Vertical: from mother to child, often in utero, or as a result of the incidental
exchange of body fluids usually during the perinatal period
— Vector transmission: indirect transmission by infected mosquitoes, mites,
flies and other insects which transmit disease to humans through their bites
— Food or water: consumption of potentially contaminated food or drinking
water.
The incubation periods for diseases are given in the additional information to facilitate the
assessment of the epidemiological link.
Viral hepatitis A
(VHA)
Case definition
Epidemiological Criteria
At least one of the following four:
— Human to human transmission
— Exposure to a common source
— Exposure to contaminated food/drinking water
— Environmental exposure
EU definitions –
case definitions for
reporting
communicable
diseases
Case classification - Cases are classified as ‘possible’, ‘probable’ and ‘confirmed’.
The incubation periods for diseases are given in the additional information to facilitate the
assessment of the epidemiological link..
A possible case means a case classified as possible for reporting purposes. It is usually a case meeting the clinical
criteria as described in the case definition without epidemiological or laboratory evidence of the disease in question.
The definition of a case as possible has high sensitivity and low specificity. It allows for detection of most cases but
some false positives cases will be included into this category.
A probable case means a case classified as probable for reporting purposes. It is usually a case with clinical criteria
and an epidemiological link as described in the case definition. Laboratory tests for probable cases are specified only
for some diseases
A confirmed case means a case classified as confirmed for reporting purposes.
Confirmed cases fall in one of the three subcategories listed below.
They will be assigned to one of those subcategories during the analysis of data using the variables collected within
the context of the case information.
Laboratory-confirmed case with clinical criteria The case meets the laboratory criteria for case confirmation and the
clinical criteria included in the case definition.
Laboratory-confirmed case with unknown clinical criteria The case meets the laboratory criteria for case confirmation
but there is no information available regarding the clinical criteria (e.g. only laboratory report).
Laboratory-confirmed case without clinical criteria The case meets the laboratory criteria for case confirmation but
doesn’t meet the clinical criteria in the case definition or is asymptomatic.
Probable case
Confirmed case
Possible case
Viral hepatitis A
(VHA)
Case definition
Case Classification
A. Possible case NA
B. Probable case
Any person meeting the clinical criteria and
with an epidemiological link
C. Confirmed case
Any person meeting the clinical and the
laboratory criteria
Outbreak
investigation
 When investigating disease outbreaks, the epidemiology profession has
developed a number of widely accepted steps:
 Identify the existence of the outbreak (Is the group of ill persons normal for
the time of year, geographic area, etc.?)
 Verify the diagnosis related to the outbreak
 Create a case definition to define who/what is included as a case
 Map the spread of the outbreak using
 Develop a hypothesis (What appears to be causing the outbreak?)
 Develop and implement control and prevention systems
 Release findings to greater communities
Study hypotheses (collect data and perform analysis)
Refine hypothesis and carry out further study
Focus of
infection
Anti-epidemic measures in the focus of
infection are carried out at the occurrence
of infection within the population.
The focus of infection is represented by
its source and its nearest neighborhood.
The introduced measures have a
repressive character.
20
Methods and possibilities of patient and convalescent carriers isolation are on so
high level - as to prevent transmission of infection to susceptible individuals
according to epidemiological severity of diseases.
Isolation of patients:
- Dpt. of infectious diseases,
- „high degree of isolation“ (ebola)
- at home,
- barriers nursing technique
SOURCE
OF INFECTION
MODE
OF TRANSMISSION
SUSCEPTIBLE
ORGANISM
Prevention of
infectious
diseases
Repressive antiepidemic
measures
Epidemiological investigation of the outbreak of the disease;
date analysis (e.g., agent, transmission, and host) and active search for
infected and suspected infections (possible sources)
Carried out immediately (preferably in an interview with the
patient), defines the scope of an outbreak of place and time.
It is necessary to trace:
 the source of infection and
other potentially infected people;
collect basic data about patients and
their contacts and
data (age, gender, onset of disease, residence, profession etc.)
 to develop epidemic curves and
expressing working hypotheses about the sources and routes of
transmission.
Guarantine
measures
Guarantine measures for suspected infection in the form of
medical supervision (regular investigation and observation after
incubation periods since the last case of the disease):
higher medical control of contacts,
laboratory screening,
focal disinfection routine around the patient for elimination EA;
final after transporting or death of the patient,
restrictions and prohibitions some profesional or private
activities,
23
SOURCE
OF INFECTION
MODE
OF TRANSMISSION
SUSCEPTIBLE
ORGANISM
HANDWASHING, DISINFECTION OF HANDS
LINEN WASHING,
CLEANING
GOOD PREPARING OF FOOD, SAFE
WATER……..,
………
DISINFECTION
STERILIZATION
Prevention of
infectious
diseases
24
Immunoprophylaxis - active and passive
immunization according to the circumstances,
chemoprophylaxis especially antibiotics or
antimalarials,
SOURCE
OF INFECTION
MODE
OF TRANSMISSION
SUSCEPTIBLE
ORGANISM
Prevention of
infectious
diseases
25
Control of basic hygiene measures , such as drinking water
, food , removal of garbage , sewage disposal,
health and educational work is the instruction of persons
affected and threatened by means of appropriate behavior.
Monitoring and evaluation of anti-epidemic measures - a
day he performs and evaluates epidemiologist , if necessary,
amend or adapt according to the situation. Efficiency measures
are evaluated from a health and economic perspective.
Measures must be viable , easily workable , understandable
and effective .
SOURCE
OF INFECTION
MODE
OF TRANSMISSION
SUSCEPTIBLE
ORGANISM
Prevention of
infectious
diseases
Viral hepatitis A
(VHA)
Case definition
 Clinical Criteria
Any person with a discrete onset of symptoms (e.g. fatigue, abdominal pain, loss of appetite,
intermittent nausea and vomiting)
 AND
At least one of the following three: * — Fever
* — Jaundice
* — Elevated serum aminotransferase levels
 Laboratory Criteria
 At least one of the following three:
 — Detection of hepatitis A virus nucleic acid in serum or stool
 — Hepatitis A virus specific antibody response
 — Detection of hepatitis A virus antigen in stool
 Epidemiological Criteria
 At least one of the following four:
 — Human to human transmission
 — Exposure to a common source
 — Exposure to contaminated food/drinking water
 — Environmental exposure
 Case Classification
 A. Possible case NA
 B. Probable case
 Any person meeting the clinical criteria and with an epidemiological link
 C. Confirmed case
 Any person meeting the clinical and the laboratory criteria
VIRAL HEPATITIS TYPEB
 RNA Picornaviridae; Single serotype worldwide
 No chronic infection; protective antibodies develop in response to infection - confers
lifelong immunity
VHA is durable; survives in the external environment cca 10 days
--------------------------------------------------------------------------------------------
Incubation period (IP): 30 – max.50 days
Infectivity period: 2 weeks at the ende IP + 1 day after after the onset of illness
the presence of high levels of virus in the faeces (10on 9 in 1 ml);
 around the onset is viremia
------------------------------------------------------------------------------------------------------
Faecal-oral transmission - Close personal contact
(e.g., household contact, sex contact, child day-care centers)
Contaminated food, water (e.g., infected food handlers)
Blood exposure (rare), (e.g., injection drug use, rarely by transfusion)
General
The source
of infection
Route of
transmission
Susceptibility
Etiology:
Hygiene (e.g., hand washing)
Preventive measures: Sanitation (e.g., clean water sources)
Hepatitis A vaccine (pre-exposure)
Immune globulin (pre- and post-exposure)
HEPATITIS A VIRUS
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Week
Response
Clinical illness
ALT
IgM IgG
HAV in stool
Infection
Viremia
EVENTS IN HEPATITIS A VIRUS INFECTION
CONCENTRATION OF HEPATITIS A VIRUS
IN VARIOUS BODY FLUIDS
Source: Viral Hepatitis and Liver Disease 1984;9-22
J Infect Dis 1989;160:887-890
Feces
Serum
Saliva
Urine
100 102
104 106 108 1010
BodyFluids
Infectious Doses per mL
GEOGRAPHIC DISTRIBUTION OF
HEPATITIS A VIRUS INFECTION
Viral hepatitis A
(VHA)
Repressive
measures
Carried out immediately (preferably in an interview with the patient), defines the
scope of an outbreak of place and time:
Guarantine measures for suspected infection in the form of medical supervision
under epidemiological characteristic:
Incubation period (IP): 30 – max.50 days
Infectivity period: 2 weeks at the ende IP + 1 day after after the onset of
illness
the presence of high levels of virus in the faeces; around the onset is viremia
A list of other potentially infected people – contacts for higher medical control:
 clinical examination
 laboratory screening: examination of antibodies IgG (distinguish susceptible
and non-susceptible persons)
by the susceptible contacts – 3 times (during 50 days after last contact with
source) examine serum aminotransferase levels.
Each increasing – reason for isolation of patient.
Viral hepatitis A
(VHA)
Repressive
measures
 focal disinfection - substanties with virucidal
efects
 active (passive ?) immunization
 prohibitions some profesional – cook
 control of basic hygiene measures , such as
hand-washing, hand- disinfection, water , food ,
removal of garbage , sewage disposal,
 health and educational work - the instruction
of potentially infected people about of appropriate
behavior.
Key characteristics of HAV, HBV, HCV, HDV, HEV
A B C D E
Causative agent
Picornaviridae Hepadnaviridae Raviviridae Deltaviridae Hepeviridae
RNA DNA RNA RNA RNA
Incubation period 2 – 6 weeks 2 - 6 months 2 - 6 months 3-7 weeks 2 - 10 weks
Characteristic of acute
hepatitis
Case fatality increases with age
Acute hepatitis more common in
adults
Acute hepatitis uncommon,
almost never fulminant
Superinfection with HDV in
chronic heptitis B may lead
to fulminnat disease
High case fatality in pregnant
women -10-20 %; other 1 -2 %
Biomarker of recent
infection
IgM anti-HAV IgM anti-HBc None IgM anti-HDV IgM anti-HEV
Chronic infection none
Chronic infection leading to
sequelae
Chronic infection leading to
sequelae
Chronic hepatitis that
copmlicated chronic
hepatitis B
Very rare
Cirrhosis and
hepatocelular Ca
No Yes; 0,1 -1,0 % are fulminant Yes; 50 % can be fulminant
Yes; 5 - 20 % can be
fulminant
NO
The period of infectivity
last 2 weeks of incubation period
last 2 months of incubation
period
last 2 months of incubation
period
?? ??first day of acute stage
entire period of acute stage entire period of acute stage
chronic disease, carriers chronic disease, carriers
Infectious biological
material
faeces blood blood blood faeces
viremia - 1. day of illnes genital secretions genital secretions meat of animals
Mode of transmission
Person-to person Perinatal Blodborne Blodborne Waterborne
Foodborne Bloodborne Perinatal Foodborne
Waterborne Sexual Sexual Person-to person
Imunization
Inactivated hepatitis A vaccines are safe
and effective for both pre- and postexposure
prophylaxis
Active (recombinant vaccine)
and passive imunization
no no
Vaccine licensed in China; not
widely available