Download Emerging Infectious Diseases:

Emerging Infections:
Assessing the risk
Dr Dilys Morgan
Health Protection Agency Centre for Infections
“The threat of apparently new or previously unrecognised
infections is ever present”
CMO, Getting Ahead of the Curve 2001
“We must do more to improve our ability to prevent, detect
and control emerging, as well as resurging, microbial threats
to health”
USA Institute of Medicine, Microbial Threats to Health;
emergence, detection and response, 2003
Global map of emerging
infections
[Morgens et al., Nature 2004]
UK definition
An emerging infectious disease can be either
• a newly recognised infectious disease,
or
• a known disease
whose reported incidence within the past 2
decades is increasing (or threatens to increase)
in a specific place, or among a specific population
Emerging infections include:
New infections resulting from changes or evolution
of existing micro-organisms
Emerging infections include:
Known infections spreading to new geographical
areas or populations
Emergence may be due to:
• Recognition of a previously undetected infection
• Realisation that an established disease has an
infectious origin (often tumours)
• Spread of a new agent
Factors driving emergence 1
Ecological changes: Economic development and land use;
agriculture; dams, changes in water ecosystems;
deforestation & reforestation; flood/drought; climate
change. [schistosomiasis, Lyme disease, RVF, Junin, hantavirus]
Factors driving emergence 2
¾
Human demographics and behaviour:
HIV, spread of dengue and of HIV and other STIs
¾
International travel and commerce:.
Dissemination of mosquito vectors, cholera into S America, V cholerae 0139
¾
Technology and industry:
E. coli 0157, BSE, transfusion assoc HBV & HCV, iatrogenic CJD
¾
Microbial adaptation and change:
Host species shift, antigenic drift in influenza, antibiotic resistant bacteria
¾
Breakdown in public health measures:
Resurgent TB and diphtheria, waterborne outbreaks of cryptosporidium
The convergence model of
emerging infectious disease
Emergence derives from interaction of the 4 domains
[Institute of Medicine, 2003]
Complex ecological
interactions
Several factors may work together or in sequence
Population movement from rural to urban; overcrowding and
poor infrastructure allows establishment of new infection;
the city itself may offer new avenues of spread
Wet markets
& integrated farming…
• Optimum conditions for amplification and spread
• Mixing and re-assortment
Emerging infections include:
Re-emerging infections - due to a reappearance
of, or increase in number of cases of a known
infection no longer considered to be a public
health problem
Global and other important
emerging Infections
HIV
• first isolated 1983
• ~20 million deaths over 20 yrs, 38 million persons infected
Hepatitis C
• identified 1989
• c 200 million chronic carriers at risk of developing liver
cirrhosis and/or cancer
vCJD
• identified 1996
• 154 cases in UK, but huge animal and human health
implications
Slow burn…….
Or
SARS
• The 1st emerging disease of the 21st century
• First cases in China Nov 2002, though not
disclosed till Feb 2003.
• International air travel = global spread
• Spread by respiratory droplets
• Animal reservoir (?)
Total probable cases – 8422
– 11%)
(deaths: 916
Detection of Emerging
infections in the UK
A combination of :
Detecting “unusual incidents”
“Horizon Scanning” and surveillance
ƒ International (global)
ƒ Locally International (Europe)
ƒ National
Threats to the UK population
- horizon scanning
) Arise in UK
) Spread of existing infections into UK
) May come from new infection arising outside UK
National Surveillance
•
Alert clinicians
•
Laboratory reports routine and reference
•
NHS Direct Symptom Surveillance
•
Primary care
with automated exceedance score alerts
•
Enhanced surveillance
•
Networks
•
Weekly teleconference
Horizon scanning
Detection of incidents/events of potential threat to
public health
Systematic review of informal and formal reports
and maintenance of log recording significant
incidents which are then followed up
“Scanning the world for informal news that gives
cause to suspect an unusual disease event”
“65% of the world’s first news about infectious
disease events now comes from informal sources
including press reports and the internet”
Heymann DL. Lancet Infectious Diseases, 2001;1:345-53
Sources for Surveillance for
Detection
Promed
CIDRAP (Centre for Infectious Diseases Research and Policy) –
University of Minnesota
WHO Disease Outbreak News
WHO Outbreak Verification List
WHO Weekly Epidemiological Record
GPHIN
MMWR
Emerging Infectious Diseases journal
Veterinary Record
Eurosurveillance
CDR
ECDC
EWRS
OIE
Scanning for emerging
risks
Monitoring &
Evaluation
Horizon
scanning
Risk
Assessment
Response
Capacity
Risk
management
Communication
Criteria to assess public
health importance
• Serious health impact
• Unexpectedly high rates of illness or death
• Potential for spread beyond national borders
• Potential for interference with international travel
or trade
• Strength of national capacity to contain outbreak
• Suspected deliberate release
Assessing the threat
Most Emerging Infections are zoonotic in origin,
and so assessing zoonotic potential of animal
infections is crucial
Human-Animal Infections and Risk
Surveillance Group
Multiagency group which meets every month and
acts as a forum to identify and discuss infections
with potential for interspecies transfer (particularly
zoonotic infections)
Human-Animal infections
and risk surveillance group
• Health Protection Agency
• Defra,
• Veterinary Laboratories Agency
• Department of Health
• Chair of National Expert Panel on New and Emerging
Infections (NEPNEI)
• Food Standards Agency
• NPHS Wales
• HP Scotland
Human-Animal Infections and
Risk Surveillance group
1 Hazard Identification
2 Risk assessment
3 Risk management
4 Risk communication
Process of risk assessment by Human-Animal Infections and Risk Surveillance
Group
Identification
by HPA, VLA,
Defra etc of
incidents with
potential for
interspecies/
zoonotic spread
Human-animal
infections and
risk surveillance
(HAIRS) Group
More detailed
preliminary assessment
following compilation of
further information and
data by HAIRS group*
Discussion and
assessment*
Negligible risk
Negligible risk
Potential risk
Minuted but no
further action
Expert Group: qualitative
risk assessment
UKZG
*using UK Surveillance
profiles when available
Include in
monthly output
Monitor (HAIRS)
Potential risk
Information and assessment communicated to
DH, HPA, FSA, UKZG, ACDP, CMO, CVO etc
Negligible risk
Statement
Monthly summaries
Infectious Disease Surveillance and Monitoring System for
Animal and Human Health: Summary of notable
events/incidents of public health significance
Monthly summary
• Avian influenza
• Ebola Zaire virus (ZEBOV), wave-like
spread, Africa
• Encephalitis, India and Nepal
• Invertebrates and emerging human
pathogens (Photorhabdus asymbiotica)
• Poliomyelitis, wild-type and vaccinederived, (update)
• Nipah virus characterisation Bangladesh
2004
• Rabies, human, vampire bats, northeast
Brazil
• Tick-borne encephalitis (TBE),
Switzerland
Assessing risk from new or
emerging infections
Probability of infection: the likelihood of an infectious
threat causing infection in the UK human population
Impact on human health: the scale of harm caused by the
infectious threat in terms of morbidity and mortality
Context: the broad environment, including public concern
and expectations, professional knowledge and external
factors including politics, in which events are occurring and
decisions on responses are being made.
Risk Assessment
New animal infection?
Expert review using template for qualitative risk assessment
• Pathogen identified?
• Equivalent disease in humans?
• Evidence to support possible zoonotic spread?
• Diagnostic tests available?
• Exposure?
• Would cases in humans be recognised?
Assessing risk from health
threats identified and reported
Assessments Î
• Need to be transparent, systematic and objective
• Used to highlight gaps in knowledge
• Used to promote risk-informed decision making
• Ensure all decisions become easier to explain and
justify
National Expert Panel for New
and Emerging Infections
The Panel’s function is to identify key areas for action and to
advise on priorities by:
• Identifying emerging and potential infectious threats to
public health both nationally and internationally
• Placing emerging infections in the wider clinical and public
health contexts
• Advising on prevention and control measures
• Prioritising areas for surveillance and for information
needs
• Advising on research, including technological development
needs
Lessons Learned
¾ Collaborative approach
¾ Rigorous risk assessment
¾ Transparency of process
¾ Risk communication
New infection…..
How would we deal with it today?
Lessons learnt from
previously emerged infections
HIV
• public perception early in epidemic was detrimental to
control
• long latent period, infectious while asymptomatic
• long incubation period - not detected early
Hepatitis C - Similar characteristics to HIV
SARS
• public panic
• rapidly symptomatic
• infectious only while symptomatic
Previously emerged
infections
¾The burdens created by new infections are
unpredictable and wide ranging
¾New infections can have a significant impact on
the UK, whether cases occur or not
¾The nature of a new infection affects its
potential to become established in the population
¾Communication and transparent risk
assessment process essential
The Future
• New emerging infections are inevitable
• Constant vigilance is required
• Expect the unexpected!