Lecture 7: Infectious Disease
- Infectious Disease
e ‘“Infectious disease” is host-centered concept
> Human body is a habitat and host to many
> Associations that harm or bother us are infectious diseases; agents (that
live inside the host) are pathogens
> Zoonosis - infectious disease transmissible to hhumans from other
animals
- Types of Pathogens (Visible to the naked eye or Invisible to naked eye)
e Worms - multicellular; parasitic
e Protozoa - unicellular; parasitic > Not visible to the naked eye needs microscope
e Bacteria - unicellular; most not parasitic
Smaller than Protozoa
vVYyYYy
Majority of them are not parasitic
They are in our stomach, which is there to help us
Aerobic vs anaerobic; or tolerate either
Some form spores ( if they are in an environment that does not support
their growth > they become dormant stage also most often cause of
ilinesses if they are caused by pathogens)
e Viruses - strand of DNA or RNA; parasitic > do not have full cells > covide is virus
> genetic material
Types of Pathogens
protozoan
virus
bacterium
RE 3.2 Approximate relative size of protozoan, bacterium, and virus.
e The Body’s Defense Against Pathogens
> |Immune system distinguishes “self” from “foreign” ( Immune system
recognises only components of our body, proteins from our body,
Foreign= also antigen > stimulates our bodies to make antibodies)
1. Active immunity - on first exposure to antigen , body produces
antibodies
> Vaccination (Used as a prevention to boost our inmmune system > to
make it stronger, Antigen and Antibody are two types of injection)
1. Antigen preparation > active immunity
- Children always get active immunity vaccination
- Weak bacteria injected > does not cause illness, causes
body to make anti-bodies > can cause reactions like fevers
[Antigen preparation]
, 2. Antibody preparation > passive immunity
- Done when we do not have time for ouur bodies to make
antibodies we inject already prepared antibodies since the
body is not making antibodies its called passive immunity
3. Covide vaccinations were completely new, it was genetic material
that was injected. It was neither antigen nor antibodies
> Herd immunity - practical protection
1. If enough members of a group are immune,hard to maintain chain
of infection
- We don’t know what exactly makes the number enough > if
enough people are vaccinated / immune to the virus its
hard for the virus to spread
e Evolution of Strategies for Managing Transmission of Disease
> Segregation of sick or exposed persons (from people who have never
been sick/ are not exposed
- Isolation: the separation of persons who have an infectious iliness
- Quarantine: the separation of persons who have been exposed to
an infectious agent
> Sanitation: beneficial
- Wash hands
- Sanitize hands
- Don’t touch eyes, nose, face
Evolution of Strategies for Managing Transmission of Disease
e Vaccination to prevent iliness
e Antibiotis to treat illness
> Population of pathogens becomes resistant over time
1. Antibodies can only kill bacterias viruses become resistant to the
antibiotics
2. Overuse of it makes some bacterias resistant too > occurs when
doctors prescribe them when not needed or not going through the
entire course
> High reproductive rates (mutate fast) allow them to become genetically
resistant quickly > Superbug > bacteria resistant to any known antibiotic
> Qveruse of antibiotics
1. Methicillin-resistant Staphylococcus aureus (MRSA)
2. Antibiotics in food additives to boost livestock (on some farms
livestocks are given antibiotics > go into the muscles of the
animals and end up on our table)
> Pesticides to control vector > mosquitos are the common vectors
,- The Transmission of Infectious Disease
e Transmission through closeness/ contact
> Droplet transmission: coughing, sneezing
1. Diptheria, tuberculosis, pertussis, influenza, measles, mumps,
rubella, COVID-19
> Direct oral contact (not just kissing)
1. Strep, herpes simplex-1, infectious mononucleosis
> Transmission by formite (object or substance capable of carrying
infectious organisms) > pink eye is an example
1. Skin cells, hair, clothing bedding
> Airbone transmission in aerosols (distinct from droplet transmission)
- Suspended in the air where goes microorganisms goes
- Not transmitted by droplet transmission
The Transmission of Infectious Disease
e Fecal-oral transmission of diarrheal disease > touching, being in contact eith
fecal source and them touching mouth the mouth (knowingly and unknowingly)
> Fecal-oral pathway: one pereson’s infectious diarrheal disease
becomenext person’s disease of fecal origin
If sewage not well contolled, waterborne transmission dominates
yVvYy
Fecal-oral transmission also via soil and by hand-to-mouth transmission
Cholera, typhoid fever, dysentery; giardiasis, crypotosporidium
(zoonoses); hepatitis A, Norwalk virus and polio
The Transmission of Infectious Diseases
e Non-fecal organisms are also transmittedin water or soil... > bacteria found in the
soil get into wound > start multiplying
> (Guinea worm disease
> Tetanus
e ....and via food (foodborne transmission)
> Housefly as mechanical vector
Global Patterns of Infectious Disease Mortality
e Fast global spreading (travelling) > earlier took months before globalisation
e Total ~ 12.3 million deaths
> Respiratory infections (29%), diarrheal disease (20%), and HIV/ AIDS
(14%) are leading infectious causes of death
e Worldwide, 22% of all deaths
> Highest in Africa (53%), South Asia (27%), and East Mediterranean (25%)
Infectious Disese as a cause of Cancer
, e Infection can increase cancer risk > not because microorganisms are carcingen
it's because of the inflammation that they cause for the long period of time
e Known infectious causes of cancer account for ~18% of cancer worldwide
> Liver (hepatitis B and C viruses, liver fluke)
> Cervix (human papilloma virus)
> Stomach (Helicobacteer pylori bacterium)
e Higher percentage in lower-income countries
20
Liver: Hepatitis B and C
ses; Opisthorchis
viverrini (Iiver fluke)
g P —
Cervix: Human papillomavirus
B
{various sublypes)
5
—— 9 | oy acterum)
69 Stomach: Helicobacter
L 38 | __— 42 Other sites: various agents
o
Industrialized countries Lower-income countries
FIGURE 3.15 Percentage of cancers caused by infectious agents in industrialized
and lower -income countrics.
Source: Data from Parkin DM. The global health burden of infection-associated cancers
in the year 2002. /nr J Cancer. 2006;118:3030-3044, Table X1
Some important Types of Pathogen (these are important from the environmental
perspective)
e Bacteria
> Tuberculosis
> Anthrax
> Plague
e \Viruses
> Yellow fever
> HIV
> Bird Flu
> West Nile Virus
e Protozoa
> Malaria
Bacterial Diseases
e Tuberculosis (immune system, food habits, where do we live enough sunshine or
not)
> Tuberculosis (TB) is one of the world’s deadliest diseases:
1. One third of the world’s population is infected with TB
2. Annually nearly 9 million people around the world become sick
with TB disease
3. Annually nearly 1.4 million TB-related (not just TB but
complications related to it) deaths worldwide
4. TB is leading killer of people who are HIV infected > people with
AIDs (Auto Immune deficiency often get TB infection)
5. Differences in health care systems > not all countries have
mandated TB vaccines
> Most commonly attacks the lungs (with discovery of antibiotics, this is
curable very long term to recovery
- Infectious Disease
e ‘“Infectious disease” is host-centered concept
> Human body is a habitat and host to many
> Associations that harm or bother us are infectious diseases; agents (that
live inside the host) are pathogens
> Zoonosis - infectious disease transmissible to hhumans from other
animals
- Types of Pathogens (Visible to the naked eye or Invisible to naked eye)
e Worms - multicellular; parasitic
e Protozoa - unicellular; parasitic > Not visible to the naked eye needs microscope
e Bacteria - unicellular; most not parasitic
Smaller than Protozoa
vVYyYYy
Majority of them are not parasitic
They are in our stomach, which is there to help us
Aerobic vs anaerobic; or tolerate either
Some form spores ( if they are in an environment that does not support
their growth > they become dormant stage also most often cause of
ilinesses if they are caused by pathogens)
e Viruses - strand of DNA or RNA; parasitic > do not have full cells > covide is virus
> genetic material
Types of Pathogens
protozoan
virus
bacterium
RE 3.2 Approximate relative size of protozoan, bacterium, and virus.
e The Body’s Defense Against Pathogens
> |Immune system distinguishes “self” from “foreign” ( Immune system
recognises only components of our body, proteins from our body,
Foreign= also antigen > stimulates our bodies to make antibodies)
1. Active immunity - on first exposure to antigen , body produces
antibodies
> Vaccination (Used as a prevention to boost our inmmune system > to
make it stronger, Antigen and Antibody are two types of injection)
1. Antigen preparation > active immunity
- Children always get active immunity vaccination
- Weak bacteria injected > does not cause illness, causes
body to make anti-bodies > can cause reactions like fevers
[Antigen preparation]
, 2. Antibody preparation > passive immunity
- Done when we do not have time for ouur bodies to make
antibodies we inject already prepared antibodies since the
body is not making antibodies its called passive immunity
3. Covide vaccinations were completely new, it was genetic material
that was injected. It was neither antigen nor antibodies
> Herd immunity - practical protection
1. If enough members of a group are immune,hard to maintain chain
of infection
- We don’t know what exactly makes the number enough > if
enough people are vaccinated / immune to the virus its
hard for the virus to spread
e Evolution of Strategies for Managing Transmission of Disease
> Segregation of sick or exposed persons (from people who have never
been sick/ are not exposed
- Isolation: the separation of persons who have an infectious iliness
- Quarantine: the separation of persons who have been exposed to
an infectious agent
> Sanitation: beneficial
- Wash hands
- Sanitize hands
- Don’t touch eyes, nose, face
Evolution of Strategies for Managing Transmission of Disease
e Vaccination to prevent iliness
e Antibiotis to treat illness
> Population of pathogens becomes resistant over time
1. Antibodies can only kill bacterias viruses become resistant to the
antibiotics
2. Overuse of it makes some bacterias resistant too > occurs when
doctors prescribe them when not needed or not going through the
entire course
> High reproductive rates (mutate fast) allow them to become genetically
resistant quickly > Superbug > bacteria resistant to any known antibiotic
> Qveruse of antibiotics
1. Methicillin-resistant Staphylococcus aureus (MRSA)
2. Antibiotics in food additives to boost livestock (on some farms
livestocks are given antibiotics > go into the muscles of the
animals and end up on our table)
> Pesticides to control vector > mosquitos are the common vectors
,- The Transmission of Infectious Disease
e Transmission through closeness/ contact
> Droplet transmission: coughing, sneezing
1. Diptheria, tuberculosis, pertussis, influenza, measles, mumps,
rubella, COVID-19
> Direct oral contact (not just kissing)
1. Strep, herpes simplex-1, infectious mononucleosis
> Transmission by formite (object or substance capable of carrying
infectious organisms) > pink eye is an example
1. Skin cells, hair, clothing bedding
> Airbone transmission in aerosols (distinct from droplet transmission)
- Suspended in the air where goes microorganisms goes
- Not transmitted by droplet transmission
The Transmission of Infectious Disease
e Fecal-oral transmission of diarrheal disease > touching, being in contact eith
fecal source and them touching mouth the mouth (knowingly and unknowingly)
> Fecal-oral pathway: one pereson’s infectious diarrheal disease
becomenext person’s disease of fecal origin
If sewage not well contolled, waterborne transmission dominates
yVvYy
Fecal-oral transmission also via soil and by hand-to-mouth transmission
Cholera, typhoid fever, dysentery; giardiasis, crypotosporidium
(zoonoses); hepatitis A, Norwalk virus and polio
The Transmission of Infectious Diseases
e Non-fecal organisms are also transmittedin water or soil... > bacteria found in the
soil get into wound > start multiplying
> (Guinea worm disease
> Tetanus
e ....and via food (foodborne transmission)
> Housefly as mechanical vector
Global Patterns of Infectious Disease Mortality
e Fast global spreading (travelling) > earlier took months before globalisation
e Total ~ 12.3 million deaths
> Respiratory infections (29%), diarrheal disease (20%), and HIV/ AIDS
(14%) are leading infectious causes of death
e Worldwide, 22% of all deaths
> Highest in Africa (53%), South Asia (27%), and East Mediterranean (25%)
Infectious Disese as a cause of Cancer
, e Infection can increase cancer risk > not because microorganisms are carcingen
it's because of the inflammation that they cause for the long period of time
e Known infectious causes of cancer account for ~18% of cancer worldwide
> Liver (hepatitis B and C viruses, liver fluke)
> Cervix (human papilloma virus)
> Stomach (Helicobacteer pylori bacterium)
e Higher percentage in lower-income countries
20
Liver: Hepatitis B and C
ses; Opisthorchis
viverrini (Iiver fluke)
g P —
Cervix: Human papillomavirus
B
{various sublypes)
5
—— 9 | oy acterum)
69 Stomach: Helicobacter
L 38 | __— 42 Other sites: various agents
o
Industrialized countries Lower-income countries
FIGURE 3.15 Percentage of cancers caused by infectious agents in industrialized
and lower -income countrics.
Source: Data from Parkin DM. The global health burden of infection-associated cancers
in the year 2002. /nr J Cancer. 2006;118:3030-3044, Table X1
Some important Types of Pathogen (these are important from the environmental
perspective)
e Bacteria
> Tuberculosis
> Anthrax
> Plague
e \Viruses
> Yellow fever
> HIV
> Bird Flu
> West Nile Virus
e Protozoa
> Malaria
Bacterial Diseases
e Tuberculosis (immune system, food habits, where do we live enough sunshine or
not)
> Tuberculosis (TB) is one of the world’s deadliest diseases:
1. One third of the world’s population is infected with TB
2. Annually nearly 9 million people around the world become sick
with TB disease
3. Annually nearly 1.4 million TB-related (not just TB but
complications related to it) deaths worldwide
4. TB is leading killer of people who are HIV infected > people with
AIDs (Auto Immune deficiency often get TB infection)
5. Differences in health care systems > not all countries have
mandated TB vaccines
> Most commonly attacks the lungs (with discovery of antibiotics, this is
curable very long term to recovery
