emerging infectious diseases paper 203
TRANSCRIPT
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Emerging & Re-emerging Infectious Diseases- Microbial health hazards
Paper-203Dr. Sneha Gang
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Outline Of Presentation
Infectious diseases- trends Definition of emerging & re-emerging
diseases Factors contributing to emergence Examples Public health response
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Infectious Disease- Trends Receded in Western countries 20th century Urban sanitation, improved housing, personal hygiene,
antisepsis (the practice of using antiseptics) & vaccination Antibiotics further suppressed morbidity & mortality Note: Morbidity refers to the unhealthy state of an individual, while mortality refers to
the state of being mortal. Both concepts can be applied at the individual level or across a population. For example, a morbidity rate looks at the incidence of a disease across a population
and/or geographic location during a single year. Mortality rate is the rate of death in a population.
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??AIDS AIDS Avian InfluenzaAvian InfluenzaEbolaEbolaMarburg Marburg CholeraCholeraRift Valley FeverRift Valley FeverTyphoidTyphoidTuberculosisTuberculosisLeptospirosisLeptospirosisMalaria Malaria ChikungunyaChikungunya DengueDengueJEJEAntimicrobial resistanceAntimicrobial resistance
UPUP
Guinea worm Smallpox
Yaws
Poliomyelitis
Measles
Leprosy
Neonatal tetanus
DOWNDOWN
Infectious Diseases: A World in Infectious Diseases: A World in TransitionTransition
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Definition Emerging infectious disease Emerging infectious diseases are diseases of infectious origin whose
incidence in humans has increased within the recent past or threatens to increase in the near future.
These also include those infections that appear in new geographic areas or increase abruptly.
The new infectious diseases and those which are re-emerging after a period of quiescence are also grouped under emerging infectious diseases.OR
Newly identified & previously unknown infectious agents that cause public health problems either locally or internationally
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Definition
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
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Factors Contributing To Emergence1. AGENT
Evolution of pathogenic infectious agents (microbial adaptation & change)
Development of resistance to drugs Resistance of vectors to pesticides
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Factors Contributing To Emergence
2. HOST Human demographic change (inhabiting new
areas) Human behaviour (sexual & drug use) Human susceptibility to infection
(Immunosuppression) Poverty & social inequality Changes in lifestyle that promote unhealthy
and risk prone behavior patterns affecting food habits and sexual practices.
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Factors Contributing To Emergence
3. ENVIRONMENT Climate & changing ecosystems Economic development & Land use (urbanization,
deforestation) Technology & industry (food processing & handling) Environmental sanitation characterized by unsafe
water supply , improper disposal of solid and liquid waste, poor hygienic practices and congested living conditions all contribute to emergence of infection
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CONTD. International travel & commerce Breakdown of public health
measure (war, unrest, overcrowding)
Deterioration in surveillance systems (lack of political will)
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Transmission of Infectious Agent from 1. Animals to Humans
>2/3rd emerging infections originate from animals- wild & domestic
Emerging Influenza infections in Humans associated with Geese, Chickens & Pigs
Animal displacement in search of food after deforestation/ climate change (Lassa fever)
Humans themselves penetrate/ modify unpopulated regions- come closer to animal reservoirs/ vectors (Yellow fever, Malaria)
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2. Climate & Environmental Changes
Deforestation forces animals into closer human contact- increased possibility for agents to breach species barrier between animals & humans
El Nino (This refers to times when waters of the tropical eastern Pacific are
colder than normal and trade winds blow more strongly than usual)- Triggers natural disasters & related outbreaks of infectious diseases (Malaria, Cholera)
Global warming- spread of Malaria, Dengue, Leishmaniasis, Filariasis
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3. Poverty, Neglect & Weakening of
Health Infrastructure Poor populations- major reservoir &
source of continued transmission Poverty- Malnutrition- Severe infectious
disease cycle Lack of funding, Poor prioritization of
health funds, Misplaced in curative rather than preventive infrastructure, Failure to develop adequate health delivery systems
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4. Uncontrolled Urbanization & Population Displacement
Growth of densely populated cities- substandard housing, unsafe water, poor sanitation, overcrowding, indoor air pollution (>10% preventable ill health)
Problem of refugees & displaced persons Diarrhoeal & Intestinal parasitic diseases,
ARILyme disease (B. burgdorferi)- Changes in ecology, increasing deer populations, suburban migration of population
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5. Human Behaviour Unsafe sexual practices (HIV, Gonorrhoea,
Syphilis) Changes in agricultural & food production
patterns- food-borne infectious agents (E. coli)
Increased international travel (Influenza) Outdoor activity
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6. Antimicrobial Drug Resistance
Causes:• Wrong prescribing practices• non-adherence by patients• Counterfeit drugs• Use of anti-infective drugs in animals
& plants
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CONTD.• Loss of effectiveness:• Community-acquired (TB,
Pneumococcal) & Hospital-acquired (Enterococcal, Staphylococcal
Antiviral (HIV), Antiprotozoal (Malaria), Antifungal
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Antimicrobial Drug Resistance
ConsequencesProlonged hospital admissionsHigher death rates from infectionsRequires more expensive, more toxic drugsHigher health care costs
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HUMAN
ANIMALS
ENVIRONMENT
VECTORSZoonosis
PopulationGrowth
Mega-cities
Migration
Exploitation
Pollution
Climate changeVectorproliferation
Vectorresistance
Transmission
Antibiotics
Intensive farming
Foodproduction
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Examples of recent emerging diseases
Source: NATURE; Vol 430; July 2004; www.nature.com/nature
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•Examples of Emerging Infectious Diseases
Hepatitis C- First identified in 1989In mid 1990s estimated global prevalence 3%
Hepatitis B- Identified several decades earlierUpward trend in all countriesPrevalence >90% in high-risk population
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CONTD. Zoonoses- 1,415 microbes are infectious for
humanOf these, 868 (61%) considered zoonotic (A zoonotic disease is a disease that can be passed between animals and humans. Zoonotic diseases can be caused by viruses, bacteria, parasites, and fungi.)70% of newly recognized pathogens are zoonoses (A zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Animals thus play an essential role in maintaining zoonotic infections in nature. Zoonoses may be bacterial, viral, or parasitic, or may involve unconventional agents.)
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Emerging Zoonoses: Human-animal interface
Marburg virus
Hantavirus Pulmonary Syndrome
Ebola virus
Borrelia burgdorferi: LymeDeer tick (Ixodes scapularis)
Mostomys rodent: Lassa fever
Avian influenza virus Bats: Nipah virus
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SARS: The First Emerging Infectious Disease Of The 21st Century
SARS Cases 19 February to 5 July 2003
China (5326)
Singapore (206)
Hong Kong (1755)
Viet Nam (63)
Europe:10 countries (38)
Thailand (9)
Brazil (3)
Malaysia (5)
South Africa (
Canada (243)
USA (72)
Colombia (1)
Kuwait (1)
South Africa (1)
Korea Rep. (3)
Macao (1)
Philippines (14)
Indonesia (2)
Mongolia (9)
India (3)
Australia (5)
New Zealand (1)
Taiwan (698)
Mongolia (9)
Russian Fed. (1)
Total: 8,439 cases, 812 deaths,30 countries in 7-8 months
Source: www.who.int.csr/sars
No infectious disease has spread so fast and far as SARS did in 2003
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Lesson learnt from SARS An infectious disease in one country
is a threat to all Important role of air travel in
international spread Tremendous negative economic
impact on trade, travel and tourism, estimated loss of $ 30 to $150 billion
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CONTD. High level commitment is crucial for
rapid containment WHO can play a critical role in
catalyzing international cooperation and support
Global partnerships & rapid sharing of data/information enhances preparedness and response
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Highly Pathogenic Avian Influenza (H5N1)
Since Nov 2003, avian influenza H5N1 in birds affected 60 countries across Asia, Europe, Middle-East & Africa
>220 million birds killed by AI virus or culled to prevent further spread
Majority of human H5N1 infection due to direct contact with birds infected with virus
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Avian Influenza/bird flu: A Viral disease of Domestic and Wild
Birds characterized by the full range of responses from almost no signs of the disease to very high mortality; caused by several subtypes of the type A strain of the influenza virus.
The incubation period is also highly variable, and ranges from a few days to a week (3 to 7 days).
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Aetiology of Avian Influenza
Influenzavirus A genus of the Orthomyxoviridae family.
They are enveloped, negative stranded RNA viruses.
Influenza A viruses can be divided into 15 Haemagglutinin (H) antigens. 9 Neuraminidase (N) antigens.
Extreme antigenic variability brought about by genetic reassortment in host cells.
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Aetiology of Avian Influenza
NOTE: Negative strand RNA viruses have a unique mechanism of
replication. Their genome is a single strand RNA that has to be transcribed as
soon as the virus enters the host in order to carry out viral replication.
As a result, a viral-specific RNA polymerase is packaged in the virion and is ready for transcription after virus entry.
This novel replication mechanism dictates the assembly and RNA synthesis of negative strand RNA viruses.
In recent years, many discoveries have been made with regard to the entry, replication and assembly of this class of viruses.
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Influenza A virus host range is polygenic
2-3Gal2-6Gal
2-3Gal
2-6Gal
2-3Gal2-6Gal
(Perez, 2006)
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H5N1 virus
electron micrograph of avian influenza H5N1 viruselectron micrograph of avian influenza H5N1 virus
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Avian Influenza
Host Range•Exotic BirdsExotic Birds •Domestic PoultryDomestic Poultry
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Avian Influenza
Peri-domestic speciesOccasional isolations of avian influenza virus from starlings and house sparrows (in contact with infected poultry)
Replication of some avian influenza virus in these species (experimental)
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2006 Avian Influenza
Natural Reservoirs of Influenza A Viruses
Wild aquatic birdsMajority are represented
by two Orders:
1. Anseriformes (ducks, geese, and swans)
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2006 Avian Influenza
Natural Reservoirs of Influenza A Viruses
2.Charadriiformes (gulls,terns, and shorebirds)
Usually show no clinical disease
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Avian Influenza
How are these viruses transmitted and maintained in these species?
Transmission: Fecal/Oral routeHeavy fecal shedding by infected ducksLong term persistence in waterIsolation of AIVs from surface water
Maintenance: Bird to birdPersistence in environment
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2006
Clinical Signs Incubation period 3-5 days Severe depression Decreased food and water
consumption Drastic decline in egg production Many birds affected Dehydration Huddling Subcutaneous swelling of the
head and neck area Nasal and oral cavity discharge
•Ruffled feathers•Swollen, cyanotic (blue) combs and wattles•Conjunctivitis with respiratory signs
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Note swollen head, and discharges.
Wattle is cyanotic and necrotic.
Huddling
Ruffled feathers
Respiratory Symptoms
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Classification Influenza viruses are
subtyped according to surface glycoproteins: hemagglutinin hemagglutinin (HA) and neuraminidase neuraminidase (NA)
Currently, there are 16 hemagglutinins (H1 to H16) and 9 neuraminidases (N1 to N9)
144 possible sub-types HemagglutininHemagglutinin attaches the
virus to the surface of the host cell so the virus can replicate
NeuraminidaseNeuraminidase lets the newly replicated viruses out of the cell to infect more cells
http://micro.magnet.fsu.edu/cells/viruses/influenzavirus.html
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What are the types of Avian Influenza in domestic poultry?
Low pathogenic avian influenza (LPAI) mild or no clinical signs low to moderate mortality However, the low pathogeniclow pathogenic H5 and H7H5 and H7 strains strains
are capable of mutating under field conditions are capable of mutating under field conditions into highly pathogenic strainsinto highly pathogenic strains
Highly pathogenic avian influenza (HPAI) sudden onset severe clinical signs high mortality
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Low Pathogenic AI
Highly Pathogenic AI
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How long can AI virus survive?
AI virus is shed in feces for 7 to 14 days after infection
AI virus can survive in manure for up to 105 days especially with high moisture and low temperature
1 gram of contaminated manure can infect 1 million birds
1 gram of manure will cover the surface of a dime
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What is the incubation period?
Usually 3 to 7 days
Depends on: strain of virus dose of inoculum age and immune
status of bird management and
environmental factors
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How does AI virus spread?
Exposure of poultry to migratory waterfowl (any bird that spends much of its life on or around a river or lake)
Exposure of commercial poultry to AI-infected backyard, gamebird, or hobby flocks
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How does AI virus spread?
Contact with AI-infected live bird markets
Dr. S. Trock Dr. S. Trock
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How does AI virus spread?
Bird to bird contact (through feces) Aerosol droplets
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How does AI virus spread?
Manure, equipment, vehicles, egg flats, crates, contaminated shoes and clothing
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How does AI virus spread?•Wildlife vectors/scavengers
Photos courtesy of G. Malone University of Delaware
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How do humans get infected with H7N9? Mainly through direct
contact with infected poultry
When people sell or slaughter and consume infected birds
Exposure during slaughter, defeathering, butchering, and preparation of poultry for cooking
So far, evidence suggests that the source of H7N9 virus is poultry and live bird markets and the most likely route of transmission from poultry to humans www.terradaily.com
www.cnn.com
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Why should we be concerned about H7N9?
H7N9 has not been previously reported in humans No background or pre-existing immunity
H7N9 is more easily transmissible from poultry to humans than H5N1 However, unlike H5N1 infections, poultry
infected with H7N9 appear healthy
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How do AI viruses change or mutate? Antigenic DriftAntigenic Drift
Occurs through small changes in the virus that happen continually over time
Produces new virus strains that may not be recognized by antibodies to earlier influenza strains
Antigenic ShiftAntigenic Shift An abrupt, major change in influenza A viruses,
resulting in a new influenza virus that can infect humans (one that has not been seen in humans for many years)
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Mutation and Reassortment 1
Reassortant HUMAN- AVIAN
virus
AVIANvirus
1. Mutation
2. Reassortment
HUMANvirus
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Mutation and Reassortment 2
Reassortant HUMAN- AVIAN
virus
AVIANvirus
1. Mutation
2. Reassortment
HUMANvirus
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Can H7N9 spread from person to person?
The spread of infection in birds increases the opportunities for direct infection of humans
Humans concurrently infected with human and avian influenza strains could serve as a “mixing mixing vesselvessel” for the emergence of a novel subtype with sufficient humans genes that can be transmitted from person to person
However, the virus has the virus has not yet developed the not yet developed the ability to pass easily ability to pass easily from human to humanfrom human to human
Avian flu Human flu
Novel flu subtype
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Diseases cycle
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Avian Influenza Infections in Humans
1997: Hong Kong (HPAI H5N1)
Infected chickens and humans
18 sick (6 died) Spread primarily from
birds to humans Person-to-person
infection noted but rare 1.5 million chickens
destroyed yaleglobal online
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Avian Influenza Infections in Humans
2003: China and Hong Kong (HPAI H5N1)
Occurred among members of a Hong Kong family that had traveled to China
1 person recovered, another died Another family member in China died Origin unknown
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Avian Influenza Infections in Humans
2013: China (H7N9) 126 cases (24 deaths) as of 29 April
2013
ecdc.europa.eu
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Pandemics are rare but deadlyPandemics are rare but deadly•1918-19 Spanish Flu (H1N1)
• 20-50 million infected worldwide • >500,000 deaths U.S.
•1957-58 Asian Flu (H2N2)• 70,000 deaths U.S.
•1968-69 Hong Kong Flu (H3N2)• 50,000 deaths U.S.
•2009-2010 Swine Flu (H1N1)• 60 million infected worldwide• 18,000 deaths
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Can another pandemic happen again? Only when three
conditions have been met: 1. a new influenza virus
subtype emerges2. it infects humans,
causing serious illness
3.3. it spreads easily and it spreads easily and sustainably among sustainably among humans*humans*
**has not yet occurred has not yet occurred with H7N9 or H5N1with H7N9 or H5N1
http://en.wikipedia.org/wiki/File:Spanish_flu_victims_burial_North_River_Labrador_1918.JPG
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What can we do to prevent AI in humans?
Practice normal hygienic precautions
Wash hands with soap and water for 15-20 seconds
Cover your mouth when you cough or sneeze
Get vaccinated for seasonal flu
Stay home and rest if you have the flu
Practice “social distancing” if there is a flu outbreak
Avoid live bird markets
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Questions?
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Highly Pathogenic Avian Influenza (H5N1)
What is the name of the bird flu? There are 16 different avian flu types.
The H5N1 strain is the one that causes the most concern, because it is the most virulent; the deadliest.
Fortunately, humans do not become easily infected with the H5N1 virus strain.
However, some highly pathogenic strains have caused severe respiratory diseases in humans
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Highly Pathogenic Avian Influenza (H5N1)
Where was Bird Flu First Discovered? Influenza A/H5N1, a severe strain of bird flu,
was first found to infect humans during poultry outbreaks in Hong Kong in 1997.
Eighteen humans were infected and six died. A mass culling of all poultry in Hong Kong may have prevented a human A/H5N1 pandemic (global epidemic) at that time.
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Highly Pathogenic Avian Influenza (H5N1)
What does the H and N stand for in flu? Influenza A viruses are divided into
subtypes based on two proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N).
There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes.
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Highly Pathogenic Avian Influenza (H5N1)
Neuraminidase enzymes are glycoside hydrolase enzymes (EC 3.2.1.18) that cleave the glycosidic linkages of neuraminic acids.
Viral neuraminidase is a type of neuraminidase found on the surface of influenza viruses that enables the virus to be released from the host cell.
Neuraminidases are enzymes that cleave sialic acid groups from glycoproteins and are required for influenza virus replication.
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Dr. KANUPRIYA CHATURVEDI
Novel Swine origin Influenza A (H1N1)
Swine flu causes respiratory disease in pigs – high level of illness, low death rates
Pigs can get infected by human, avian and swine influenza virus
Occasional human swine infection reported
In US from December 2005 to February 2009, 12 cases of human infection with swine flu reported
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Swine Flu Influenza A (H1N1)
March 18 2009 – ILI outbreak reported in Mexico
April 15th CDC identifies H1N1 (swine flu) April 25th WHO declares public health
emergency April 27th Pandemic alert raised to phase 4 April 29th Pandemic alert raised to phase 5 NOTE- A pandemic is the worldwide spread of a new disease
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Dr. KANUPRIYA CHATURVEDI
Influenza A (H1N1) By May 5th more than 1000 cases confirmed in
21 countries Screening at airports for flu like symptoms
(especially passengers coming from affected area)
Schools closed in many states in USA May 16th India reports first confirmed case Stockpiling of antiviral drugs and preparations to
make a new effective vaccine
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Dr. KANUPRIYA CHATURVEDI 74
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Dr. KANUPRIYA CHATURVEDI
Pandemic HINI (Swine flu) Worldwide- 162,380 cases
1154 deaths
India- 558 cases1 death
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Dr. KANUPRIYA CHATURVEDI
Examples of Re-Emerging Infectious Diseases
Diphtheria- Early 1990s epidemic in Eastern Europe(1980- 1% cases; 1994- 90% cases)
Cholera- 100% increase worldwide in 1998 (new strain eltor, 0139)
Human Plague- India (1994) after 15-30 years absence. Dengue/ DHF- Over past 40 years, 20-fold increase to nearly 0.5 million (between 1990-98)
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Dr. KANUPRIYA CHATURVEDI
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Dr. KANUPRIYA CHATURVEDI
Bioterrorism
Possible deliberate release of infectious agents by dissident individuals or terrorist groups
Biological agents are attractive instruments of terror- easy to produce, mass casualties, difficult to detect, widespread panic & civil disruption
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Dr. KANUPRIYA CHATURVEDI
CONTD. Highest potential- B. anthracis, C.
botulinum toxin, F. tularensis, Y. pestis, Variola virus, Viral haemorrhagic fever viruses
Likeliest route- aerosol dissemination
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Dr. KANUPRIYA CHATURVEDI
Key Tasks in Dealing with Emerging Diseases
Surveillance at national, regional, global level epidemiological, laboratory ecological anthropological
Investigation and early control measures Implement prevention measures
behavioural, political, environmental Monitoring, evaluation
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Dr. KANUPRIYA CHATURVEDI
National surveillance:current situation
Independent vertical control programmes
Surveillance gaps for important diseases
Limited capacity in field epidemiology, laboratory diagnostic testing, rapid field investigations
Inappropriate case definitions
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Dr. KANUPRIYA CHATURVEDI
CONTD. Delays in reporting, poor analysis
of data and information at all levels
No feedback to periphery Insufficient preparedness to control
epidemics No evaluation
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Dr. KANUPRIYA CHATURVEDI
Solutions
Public health surveillance & response systems Rapidly detect unusual, unexpected,
unexplained disease patterns Track & exchange information in real time Response effort that can quickly become
global Contain transmission swiftly & decisively
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Dr. KANUPRIYA CHATURVEDI
GOARNGlobal Outbreak Alert & Response Network Coordinated by WHO Mechanism for combating international
disease outbreaks Ensure rapid deployment of technical
assistance, contribute to long-term epidemic preparedness & capacity building
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Dr. KANUPRIYA CHATURVEDI
Sharing Outbreak-related Sharing Outbreak-related InformationInformation• with Public Health Professionalswith Public Health Professionals
• with Publicwith Public
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Dr. KANUPRIYA CHATURVEDI
Solutions
Internet-based information technologiesImprove disease reportingFacilitate emergency communications &Dissemination of information
Human Genome ProjectRole of human genetics in disease susceptibility, progression & host response
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Dr. KANUPRIYA CHATURVEDI
Solutions
Microbial geneticsMethods for disease detection, control & preventio
Improved diagnostic techniques & new vaccines Geographic Imaging Systems
Monitor environmental changes that influence disease emergence & transmission
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Dr. KANUPRIYA CHATURVEDI
Key tasks - carried out by whom?
National
RegionalGlobal
Synergy
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Dr. KANUPRIYA CHATURVEDI
What skills are needed?
Multiple expertise neededMultiple expertise needed !
Infectious diseases
Epidemio-logy
Public Health
International field
experience Information management
Laboratory
Telecom. & Informatics
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Dr. KANUPRIYA CHATURVEDI
Global Disease Intelligence: A world on the alert
CollectionCollection
VerificationVerification DistributionDistribution
ResponseResponse
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Dr. KANUPRIYA CHATURVEDI
The Best Defense (Multi-factorial)
Coordinated, well-prepared, well-equipped PH systems
Partnerships- clinicians, laboritarians & PH agencies
Improved methods for detection & surveillance
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Dr. KANUPRIYA CHATURVEDI
CONTD. Effective preventive & therapeutic
technologies Strengthened response capacity Political commitment & adequate
resources to address underlying socio-economic factors
International collaboration & communication