Emerging infectious diseases paper 203

Emerging & Re-emerging Infectious Diseases- Microbial health hazards

Paper-203Dr. Sneha Gang

Outline Of Presentation

Infectious diseases- trends Definition of emerging & re-emerging

diseases Factors contributing to emergence Examples Public health response

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.

??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

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

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

Factors Contributing To Emergence1. AGENT

Evolution of pathogenic infectious agents (microbial adaptation & change)

Development of resistance to drugs Resistance of vectors to pesticides

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.

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

CONTD. International travel & commerce Breakdown of public health

measure (war, unrest, overcrowding)

Deterioration in surveillance systems (lack of political will)

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)

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

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

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

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

6. Antimicrobial Drug Resistance

Causes:• Wrong prescribing practices• non-adherence by patients• Counterfeit drugs• Use of anti-infective drugs in animals

& plants

CONTD.• Loss of effectiveness:• Community-acquired (TB,

Pneumococcal) & Hospital-acquired (Enterococcal, Staphylococcal

Antiviral (HIV), Antiprotozoal (Malaria), Antifungal

Antimicrobial Drug Resistance

ConsequencesProlonged hospital admissionsHigher death rates from infectionsRequires more expensive, more toxic drugsHigher health care costs

HUMAN

ANIMALS

ENVIRONMENT

VECTORSZoonosis

PopulationGrowth

Mega-cities

Migration

Exploitation

Pollution

Climate changeVectorproliferation

Vectorresistance

Transmission

Antibiotics

Intensive farming

Foodproduction

Examples of recent emerging diseases

Source: NATURE; Vol 430; July 2004; www.nature.com/nature

http://www.nature.com/nature

•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

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.)

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

http://en.wikipedia.org/wiki/Image:Pteropus_vampyrus1.jpg

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

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

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

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

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).

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.

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.

Influenza A virus host range is polygenic

2-3Gal2-6Gal

2-3Gal

2-6Gal

2-3Gal2-6Gal

(Perez, 2006)

H5N1 virus

electron micrograph of avian influenza H5N1 viruselectron micrograph of avian influenza H5N1 virus

Avian Influenza

Host Range•Exotic BirdsExotic Birds •Domestic PoultryDomestic Poultry

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)

2006 Avian Influenza

Natural Reservoirs of Influenza A Viruses

Wild aquatic birdsMajority are represented

by two Orders:

1. Anseriformes (ducks, geese, and swans)

2006 Avian Influenza

Natural Reservoirs of Influenza A Viruses

2.Charadriiformes (gulls,terns, and shorebirds)

Usually show no clinical disease

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

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

Note swollen head, and discharges.

Wattle is cyanotic and necrotic.

Huddling

Ruffled feathers

Respiratory Symptoms

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

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

Low Pathogenic AI

Highly Pathogenic AI

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

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

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


Contact with AI-infected live bird markets

Dr. S. Trock Dr. S. Trock


Bird to bird contact (through feces) Aerosol droplets


Manure, equipment, vehicles, egg flats, crates, contaminated shoes and clothing

How does AI virus spread?•Wildlife vectors/scavengers

Photos courtesy of G. Malone University of Delaware

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

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

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)

Mutation and Reassortment 1

Reassortant HUMAN- AVIAN

virus

AVIANvirus

1. Mutation

2. Reassortment

HUMANvirus

Mutation and Reassortment 2

Reassortant HUMAN- AVIAN

virus

AVIANvirus

1. Mutation

2. Reassortment

HUMANvirus

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

Diseases cycle

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


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


2013: China (H7N9) 126 cases (24 deaths) as of 29 April

2013

ecdc.europa.eu

http://www.google.com/url?sa=i&rct=j&q=h7n9+avian+influenza&source=images&cd=&cad=rja&docid=TIAb1JkCjcZCkM&tbnid=XCs-fJ0edByKVM:&ved=0CAQQjB0&url=http%3A%2F%2Fecdc.europa.eu%2Fen%2Fpress%2Fnews%2FLists%2FNews%2FDispForm.aspx%3FID%3D902&ei=2dh_Uea_ELGp4AO-14GoBQ&bvm=bv.45645796,d.dmg&psig=AFQjCNFudFLABKhwWHw-uUwyQfaz6bCrdw&ust=1367419376344047

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

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

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

Questions?


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


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.


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.


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.

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

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


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

Dr. KANUPRIYA CHATURVEDI 74


Pandemic HINI (Swine flu) Worldwide- 162,380 cases

1154 deaths

India- 558 cases1 death


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)



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


CONTD. Highest potential- B. anthracis, C.

botulinum toxin, F. tularensis, Y. pestis, Variola virus, Viral haemorrhagic fever viruses

Likeliest route- aerosol dissemination


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


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


CONTD. Delays in reporting, poor analysis

of data and information at all levels

No feedback to periphery Insufficient preparedness to control

epidemics No evaluation


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


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


Sharing Outbreak-related Sharing Outbreak-related InformationInformation• with Public Health Professionalswith Public Health Professionals

• with Publicwith Public


Solutions

Internet-based information technologiesImprove disease reportingFacilitate emergency communications &Dissemination of information

Human Genome ProjectRole of human genetics in disease susceptibility, progression & host response


Solutions

Microbial geneticsMethods for disease detection, control & preventio

Improved diagnostic techniques & new vaccines Geographic Imaging Systems

Monitor environmental changes that influence disease emergence & transmission


Key tasks - carried out by whom?

National

RegionalGlobal

Synergy


What skills are needed?

Multiple expertise neededMultiple expertise needed !

Infectious diseases

Epidemio-logy

Public Health

International field

experience Information management

Laboratory

Telecom. & Informatics


Global Disease Intelligence: A world on the alert

CollectionCollection

VerificationVerification DistributionDistribution

ResponseResponse


The Best Defense (Multi-factorial)

Coordinated, well-prepared, well-equipped PH systems

Partnerships- clinicians, laboritarians & PH agencies

Improved methods for detection & surveillance


CONTD. Effective preventive & therapeutic

technologies Strengthened response capacity Political commitment & adequate

resources to address underlying socio-economic factors

International collaboration & communication

Science

Emerging infectious diseases paper 203