MICR 454L

1
MICR 454L

• Emerging and Re-Emerging
• Infectious Diseases
• Lecture 1 Identifying the Problem
• Dr. Nancy McQueen Dr. Edith Porter

2
Overview the course

• Course requirements and challenge for the
  students
• Quizzes
• Midterm
• Research paper presentation and discussions
• Hot topics presentations
• Case studies
• Comprehensive final exam

3
The Problem
Emerging and Re-emerging Infectious diseases
4
Overview the problem

• Identifying the problem
• Factors responsible for emerging infections
• World population growth
• Urbanization
• Ecological disturbances
• Technological advances
• Microbial evolution and adaptation
• Human behavior and attitudes

5
The problem of emerging infections

• The problem is a worldwide challenge by microbes
  whose survival is linked to ours
• The vast majority of microbes are beneficial
• The small minority of microbes that produce
  disease are called pathogens.
• History of the problem
• From the 1950s through the 1970s microbial
  diseases appeared to be on their way out
• Vaccinations
• Antibiotics and other antimicrobics
• Improved world economy and decreased poverty
• However, from 1980 to 1992 the CDC reported a 22
  increase (excluding AIDS) in infectious diseases

6
The problem of emerging infections

• In 1996, published data indicated that since 1980
  there was a greater than 50 increase in deaths
  caused by microbes in the United States.
• Emerging infections are defined as those
  infections whose incidence in humans has
  increased in the past two decades or will
  increase in the future.
• Emerging infections can be defined as
• New
• Reemerging
• Drug resistant infections
• Emergence is a two step process
• Introduction of the infectious agent into a new
  population. The agent may be
• Already present
• Located within another species
• A variant of an existing pathogen
• Dissemination of the infectious agent
• What are some of these emerging infections?

7
Emerging and Re-emerging Infectious Diseases
avian
Red names are newly emerging infectious diseases
Blue names are re-emerging infectious diseases
Black names are emerging bioterrorism infectious
diseases Names circled in green are RNA
viruses Adapted from Morens, D. M., et al. 2004.
The Challenge of Emerging and Re-emerging
Infectious Diseases. Nature 430 242-249
8
Recent outbreaks of infectious diseases
9
Leading causes of death
Leading causes of death,1998. There were 53.9
million deaths world-wide in 1998. Cancers,
cardiovascular, and respiratory and digestive
diseases can also be caused by infections. Thus
, the percentage of deaths due to infectious
diseases may be even higher than shown. (Source
WHO report, 1999.)
10
Leading causes of death in Africa versus the
Americas
Causes of death in the Americas and Africa, 2002,
by percentage of cause.There were 10.7 million
deaths in Africa, 6.7 million due to infectious
diseases. There were 6 million deaths in the
Americas, 623,000 due to infectious diseases.
Intentional deaths include murder suicide, and
war.
11
Leading infections disease killers

Leading infectious killers. The graph shows
millions of deaths world-wide in 1998 for persons
of all ages. Pneumonia and influenza are
included in acute respiratory infections. Deaths
among HIV-positive individuals with tuberculosis
are included under AIDS. (Source WHO report,
1999.
12
Factors responsible for emerging diseases

• World population growth most important
• Urbanization (changes in demographics)
• Ecological disturbances
• Deforestation disturbances to natural habitat
• Climate changes
• Natural disasters (drought, flooding)
• Technical advances
• Air travel
• Unsafe blood supplies
• Human behavior and attitudes
• Complacency
• Migration
• Societal factors
• Microbial evolution and adaptation
• Antimicrobial resistance
• Evasive strategies

13
World population growth
World population, 1950 to 2050. Projections are
based on an estimated annual growth rate of
1.25. (Source U.S. Census Bureau, International
Dada Base, May 10, 2000.
14
World population growth is central to the issue
15
How does increased population result in an
increase of infectious diseases?

• Increased transmission
• Population density
• Person to person transmission is facilitated by
  population density increases
• Distribution of the population
• The elderly are more susceptible to disease and
  can serve as a source of infection
• Other potential effects
• Greater likelihood of global warming
• Larger numbers of travelers
• More frequent wars
• Increased numbers of refugees and internally
  displaced persons

16
How does increased population result in an
increase of infectious diseases?

• Increased hunger and malnutrition
• More crowded living in urban slums
• Increased numbers of people living in poverty
• Inadequate potable water supply
• More large dam construction and irrigation
  projects

17
Urbanization

• In the past 50 years, about 25 of the population
  have left their rural environment for the cities
• By 2030, more than 75 of the worlds population
  will live in cities

5 billion
2.5 billion
750 million
240 million
Progressive urbanization of out planet. The
different colors for 2030 indicate proportions of
urban population that are projected to live in
developed countries (20) and underdeveloped
countries (80)
18
Urbanization

• The magnitude of the effect of urbanization on
  infectious diseases depends upon
• Economy of the country
• Public health infrastructure necessary to cope
  with the increasing population density

19
Slums and shanty towns. Poverty is associated
with a lack of sanitary facilities, an increase
in rodent populations, a lack of safe drinking
water, and other circumstances that contribute to
infectious diseases
20
Urbanization

• Emergence of diseases due to urbanization
• Dengue fever is caused by a flavivirus
• Causes Dengue fever and Dengue hemorrhagic fever
• Is transmitted by Aedes mosquitoes that are
  unable to fly long distances
• Houseto-house infestation of the mosquito occurs
  in cramped urban living conditions
• Disease has moved into the U.S. as the virus
  infects a different species of Aedes mosquito
• West Nile virus is also caused by a flavivirus
• Is also transmitted by a mosquito vector
• First identified in the U.S. in New York City in
  1999.

21
Spread of WNV in the United States
22
Even in developed countries urbanization often
leads to poverty and disease
23
Ecological disturbances

• Deforestation

Deforestation. As people move into and/or develop
agriculture in areas that were formerly forests,
there is increased contact with animals,
including insects, that harbor infectious
microbes. In search of food, the displaced
animals return to neighborhoods that were once
their lands.
24
Ecological disturbances

• Deforestation
• Eastern U.S.
• Raccoons foraging for food ? ?rabies (zoonotic
  disease - transmitted from animal to human)
• Lyme, Connecticut in 1970s
• Intersection of humans with rodent-deer life
  cycle of B. burgdorferi infected ticks ?
  emergence of Lyme disease
• Guanarito region of central Venezuela
• Humans in contact with excretions of infected
  rodents ? ? Venezuelan hemorrhagic fever
• Central railroad in Brazil
• Indigenous mammals displaced? Kissing bugs
  feeding on humans ? ?Chagas disease
• Aswan High Dam in Egypt
• New snail habitat ? ?schistosomiasis
• Aswan High Dam in Egypt
• ?Flood lands ? ?Mosquitoes ? ?Rift valley fever

25
Ecological disturbances - Deforestation
A village with a high incidence of leishmaniasis.
Leishmaniasis is a protozoan infection
transmitted by infected sand flies. Sand flies
are poor fliers, but they can traverse the short
distance from their forest habitat.
Leishmania
26
Deforestation
The interspecies leap. AIDS, which originated in
Africa, is presumed to have jumped the species
barrier from infected monkeys to humans.
HIV
27
Ecological disturbances

• Climatic changes including global warming may
  favor the outbreak of many infectious diseases
• Vibrio parahaemolyticus - ocean borne
• Malaria - mosquitoes
• Rift Valley fever - mosquitoes
• Hantavirus - mice
• Cholera - waterborne
• Hepatitis - waterborne
• Lyme disease - ticks
• Dengue fever - mosquitoes
• Cryptosporidosis - waterborne

28
Ecological disturbances

• Climatic changes are likely to particularly
  effect vector-borne diseases (diseases carried to
  humans by arthropods)
• May effect the vector
• May effect the microbe

Disease Population at risk, millions Prevalence of infection Present distribution Possible change of distribution as a result of climatic change
Malaria 2,100 270 million Tropics, subtropics Highly likely
Lymphatic filariasis 900 90.2 million Tropics, subtropics Likely
Onchocersiasis 90 17.8 million Africa, Latin America Likely
Schistosomiasis 600 200 million Tropics, subtropics Very likely
African trypanosomiasis 50 25,000 new cases per year Tropical Africa Likely
Leishmaniasis 350 12 million infected 400,000 new cases per year Asia, Southern Europe, Africa, South America Not known
Dracunculiasis 63 1 million Tropics (Africa, Asia) Unlikely
Arboviral diseases
Dengue NA NA Tropics, subtropics Very likely
Yellow fever NA NA Africa, Latin America Likely
Japanese encephalitis NA NA East and Southeast Asia Likely
Other arboviral diseases NA NA Tropical to temperate zones Likely
29
Ecological disturbances

• Natural disasters
• Flooding ??malaria and cholera in Africa
• Drought ? famine ? ?disease in Africa
• Increased humidity ??crop of pine needles? ?mouse
  deer population?emerging Hantavirus infections in
  Four Corners area of U.S.

30
Technological advances

• International travel SARS, penicillin-resistant
  gonorrhea, monkeypox

Approximate flying time from New York City
Sydney, Australia 22 hours (1 stop)
Tokyo, Japan 14 hours (nonstop)
Tel Aviv, Israel 10 hours (nonstop)
Nairobi, Kenya 16 hours (1 stop)
Incubation period for selected diseases
Whooping cough 7-10 days
Gonorrhea 2-6 days
Salmonella food poisoning 8-48 hours
Ebola fever 4-16 days
Measles 12-32 days
Chicken pox 10-23 days
Its a small world after all. In a span of a
couple of days, President Bill Clinton
demonstrated the truth of this cliché. He flew
from Washington to New York and back. Then he
flew to Cincinnati, Denver, and Aspen. After
briefly returning to Washington again, he flew to
Morocco. From there he returned to Washington
one more time. All that travel took place in one
weekend.
31
Technological advances

• Blood transfusions - hepatitis, HIV, malaria,
  trypanosomiasis, syphilis, Chagas disease.
• Organ transplants and immunosuppressive drugs -
  CMV,
• mad cow disease

32
Microbial evolution and adaptation

• Antimicrobic resistance
• In the last 50 years antibiotics and
  antimicrobics have saved the lives of innumerable
  individuals with infections
• However now the microbes are becomimg resistant
  to antimicrobics - why?
• GROSS MISUSE of antimicrobics

33
Microbial evolution and adaptation

• Development of antimicrobic resistance

Developing countries
Developed countries
Insufficient use of antimicrobics Too
expensive Save it for a rainy day
Failure to complete dose
Overuse of antimicrobics Available virtually
on demand Used when not necessary Failure
to complete dose
Antimicrobic resistance
34
Emergence of antimicrobial drug resistant bacteria
35
Increasing resistance of selected pathogens
Methicillin resistant Staphylococcus aureus
36
Microbial evolution and adaptation
Examples of drug-resistant diseases
Bacterial disease Viral disease Protozoan disease
Typhoid fever HIV infection Malaria
Tuberculosis Hepatitis B Visceral leishmaniasis
Gonorrhea
Staphylococcal infection
Shigellosis
Pneumococcal infection
Enterococcal infection
37
Microbial evolution and adaptation

• Microbes change their surface structures to evade
  host defenses Vibrio cholera

Antibody cant bind to antigen
Antibody can bind to antigen
Changing ones coat. Trypanosomes and other
microorganiams can form new surface antigens not
recognized by antibodies. This is an important
evasion strategy.
38
Microbial evolution and adaptation

• Acquisition of new proteins introduced by
  lysogenic bacteriophages
• Toxins produced by Streptococcus pyogenes that
  lead to necrotizing fasciitis (flesh eating
  bacteria).
• Mutations and evolution of viruses.
• Mainly RNA viruses
• Include Ebola virus, SARS virus, Hantavirus,
  Avian influenza virus
• More on this later
• Adaptation of insect vectors
• Mosquitoes become resistant to DTT
• Malaria
• ? West Nile virus

39
Human behavior and attitudes

• Complacency - it cant happen to me
• Return to risky sexual behavior and ?AIDS and
  gonorrhea
• Failure to immunize your children - measles
• Failure to get immunizations when traveling to
  foreign countries - yellow fever and malaria

40
Human behavior and attitudes

• Human migration -wars and conflicts resulting
  from political differences result in refugees or
  internally displaced persons who move from one
  part of the country to another

A refuge camp. Refuge camps are hotbeds of
infection. Crowding and lack of hygiene and
sanitation favor the incidence and transmission
of disease
41
Human behavior and attitudes

• Societal factors
• Increased numbers of women workers ??in child
  care centers
• Intestinal parasites
• Diarrhea
• Middle ear infections
• Meningitis
• Increased longevity??nursing homes, day care
  centers for adults, and assisted living
  environments
• Food production and dietary habits lead to ?
  food-borne diseases
• Centralized food processing E. coli from spinach
  
• Fast food and take-out restaurants
• Import of agricultural produce - hepatitis A from
  strawberries and onions from Mexico, Cyclospora
  from Guatamalan raspberries

42
Human behavior and attitudes

• Tattooing and body piercing and Staphylococcus
  aureus infections

Tattooing and skin piercing. Tattooing and skin
piercing are a risky part of popular culture.
The skin is invaded, potentially resulting in
serious infection because of he use of unclean
instruments
43
Take Home Message

• Infectious disease deaths decreased from the
  1950s through the 1970s.
• Infectious disease deaths started to rise again
  in the 1980s.
• New, emerging, and reemerging infections are a
  major health problem today.
• The world population growth is central to the
  issue of emerging infections. Other contributing
  factors include
• Urbanization
• Ecological disturbances
• Technological advances
• Microbial evolution and adaptation
• Human behavior and attitudes

44
Resources

• The Microbial Challenge, by Krasner, ASM Press,
  Washington DC, 2002.
• Brock Biology of Microorganisms, by Madigan and
  Martinko, Pearson Prentice Hall, Upper Saddle
  River, NJ, 11th ed, 2006.
• Microbiology An Introduction, by Tortora, Funke
  and Case Pearson Prentice Hall 9th ed, 2007.
• Emerging Infectious Diseases. Michael A.
  Palladino, series editor Benjamin Cummings
  speical topics in biology, 2006.