EMERGING AND RE-EMERGING

INFECTIOUS DISEASES

IMPORTANT TERMS• Emerging infectious disease- An infectious disease that has newly appeared in a

population or that has been known for some time but is rapidly increasing in incidence or geographic range.

• Re-emerging infectious disease- diseases that once were major health problems globally or in a particular country, and then declined dramatically, but are again becoming public health problems for a significant proportion of the population.

• Infectious diseases- are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the diseases can be spread, directly or indirectly, from one person to another.

• Zoonotic diseases- are infectious diseases of animals that can cause disease when transmitted to humans.

INTRODUCTION

• In developing countries where much of the population lives in conditions of extreme poverty, infectious diseases remain the leading cause of death

• In the U.S., prevention and control of infectious diseases have been so successful in the past half century that many people view infectious diseases as either a thing of the past or minor illnesses easily treated and cured

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http://www.who.int/mediacentre/factsheets/fs310/en/index1.html

CAUSES OF DEATH IN HIGH- INCOME COUNTRIES (2012)

http://www.who.int/mediacentre/factsheets/fs310/en/index1.html

CAUSES OF DEATH IN LOW- INCOME COUNTRIES (2012)

EXAMPLES OF EMERGING INFECTIOUS DISEASES

• Ebola virus (first outbreaks in 1976 and the discovery of the virus in 1977)

• HIV/AIDS (virus first isolated in 1983)

• Hepatitis C (first identified in 1989, now known to be the most common cause of post-transfusion hepatitis worldwide)

• Influenza A(H5N1) virus (well known pathogen in birds but first isolated from humans in 1997)

EXAMPLES OF EMERGING INFECTIOUS DISEASES

• Legionella pneumophila (first outbreak in 1976 as Legionnaire disease and since associated with similar outbreaks linked to poorly maintained air conditioning systems)

• E. coli O157:H7 (first detected in 1982, often transmitted through contaminated food, has caused outbreaks of hemolytic uremic syndrome)

• Borrelia burgdorferi (first detected in 1982 and identified as the cause of Lyme disease)

• Severe Acute Respiratory Syndrome (SARS) (first detected in 2003 in Asia); the first emerging infectious disease of the 21st century

• Swine Flu Influenza A (H1N1) (first observed in 2009 in Mexico)

EBOLA• Has a fatality rate of 50-90%

• Experts continue the fight to control the Ebola haemorrhagic outbreak in western Uganda. The outbreak, now in its second week, has claimed at least 16 lives out of 53 cases reported. Ebola is caused by one of the most virulent pathogens known to humankind (WHO, 2012).

• No specific treatment or vaccine is yet available for EHF. New drug therapies have shown promising results in laboratory studies and are currently being evaluated. Several vaccines are being tested but it could be several years before any are available.

E. COLI 0157:H7

• E. coli 0157:H7- More deadly strain appeared in 1982• passed from person to person (in

feces)• contaminated food, contaminated

water or other liquid• Raw milk

• In 1993 Washington State• Jack –in-the-Box hamburgers• Outbreak killed 4 children and 700 persons became ill

As of March 21, 2012, 58 persons infected with the outbreak strain of E. coli O157:H7 (associated with Romaine Lettuce) were reported from 9 states. The number of ill persons identified in each state was as follows: Arizona (1), Arkansas (2), Illinois (9), Indiana (2), Kansas (2), Kentucky (1), Minnesota (2), Missouri (38), and Nebraska (1). This particular outbreak appears to be over and consumers are not being advised to avoid eating any specific foods at this time.

FACTORS INVOLVED IN THE EMERGENCE OF INFECTIOUS DISEASES

1. Unprecedented worldwide population growth, urbanization

2. Increased international travel

3. Increased worldwide transport, migration, and relocation of animals and food products

4. Changes in food processing, handling, and agricultural practices

5. Changes in human behaviour, technology and industry

6. Human encroachment on wilderness habitats that are reservoirs for insects and animals that harbour infectious agents

FACTORS INVOLVED IN THE EMERGENCE OF INFECTIOUS DISEASES7. Microbial evolution and the development of resistance to antibiotics and other antimicrobial

drugs

8. Changes in ecology and climate

9. Modern medicine (e.g. immunosuppression), human susceptible to infection

10. Inadequacy of public infrastructure and vaccination programs

11. Social unrest and civil wars

12. Bioterrorism

13. Virulence-enhancing mechanism of pathogens (the mobile bacteriophages, plasmids, transposons)

INFECTIOUS DISEASES ON THE RISE

• Many diseases thought to be adequately controlled appear to be making a “comeback”

• In developed countries, public health measures such as sanitation, sewage treatment, vaccination programs, and access to good medical care have virtually eliminated “traditional” diseases such as: • Diptheria, whooping cough, and tuberculosis

• Many of these diseases are becoming a public health problem once again, as immunization programs and other public standards are enforced less vigorously and, as antibiotic resistant pathogens evolve

INFECTIOUS DISEASES ON THE RISE

• Strains of pneumonia-caused by Staphylococcus aureus are resistant to all of the currently available drug treatments

• Among the diseases “reemerging” as a consequence of microbial resistance are:

• Tuberculosis, and malaria, leading causes of death from infectious diseases worldwide

INFECTIOUS DISEASES ON THE RISE• Global spread of AIDS• Resurgence of tuberculosis• Appearance of new enemies (hantavirus, hepatitis C and E, Ebola virus,

Lyme disease, cryptosporidiosis and E. coli O157:H7• Bird flu which attacks the Southeast Asia• Prion disease of Creutzfeldt-Jakob disease• Antibiotic resistance Staphylococcus bacteria• Several major multistate foodborne outbreaks• Whooping cough (pertussis)• A new strain of drug resistance tuberculosis

WHOOPING COUGH (PERTUSSIS)• Whooping cough—or pertussis—is a very serious respiratory (in the lungs and breathing tubes)

infection caused by bacteria. It causes violent coughing you can’t stop. Whooping cough is most harmful for young babies and can be deadly.

• Among vaccine-preventable diseases, (the DTaP vaccine protects against whooping cough), pertussis is one of the most commonly occurring ones in the United States.

• In Washington, there have been 3,285 cases reported statewide through July 28, 2012, compared to 253 reported cases in 2011 during the same time period. There were 965 cases reported statewide in 2011 compared to 608 reported cases in 2010. Visit the Washington State Department of Health for the most recent information.

• In 2011 and the start of 2012, an increase in pertussis cases has been reported in Argentina1, Colombia2, Chile3, Canada and the USA,4 with cases predominantly in adolescents and newborns.

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

POSSIBLE 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

• Questions??