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Summary All Lectures of Containment Strategies
- Instelling
- Vrije Universiteit Amsterdam (VU)
Notes from all the lectures given in the course Containment strategies of infectious diseases in a global context.
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Lectures Containment StrategiesHC Sep 4. Introduction
In the late medieval period bubonic plague killed 1/3 of the European population. Plague is the first
infectious disease with a big containment strategy. In Venice they started with quarantine measures.
Ships had to wait 40 days before the crew and goods could come to land.
Quarantine: isolating all people that are or might be infected with a certain disease.
Isolation: only isolating everyone who is ill.
The Spanish flu (1918) killed over 50-100 million people worldwide, 1/3 of the world population was
infected. Quarantine led to less affected areas, e.g. Japan.
In 1928, Alexander Fleming discovered penicillin, the first antibiotic.
In 1796, Edward Jenner discovered that vaccinating people with cow pox makes them immune to
smallpox. In 1953, the Dutch Vaccination Program EPI starts. Vaccination is one of the most successful
developments in the control, elimination and eradication of infectious diseases. However, there is
more and more societal resistance.
When HIV/AIDS developed as a global disease, multiple containment approaches were used (e.g.
micro credits, self-help groups, global fund, treatment campaigns).
5 intervention steps of Jenkins
1. What is the problem (is it a priority health problem)?
2. What factors cause the problem?
3. How can these factors be changed?
4. What overall intervention strategies are most appropriate and cost effective (including what
do people want and what are their needs?)?
5. What needs to be done to reach the goals? With what (sub)populations shall work be done,
and in what sequence, to solve the problem?
HC Sep 5. Basic Immunology
Immunology is the study of host defence mechanisms. Immunity is the ability of the host to protect
itself against foreign organism. The immune system comprises the tissue, cells, and molecules which
mount the immune response.
Natural ( ‘innate’ ) immune system is nonspecific and property of all living creatures. It is the first line
of defence, and contains physical and chemical defences: skin, tears, saliva, mucus, acids.
Adaptive ( ‘acquired’ ) immune system is the second line of defence. And includes specialist cells,
cytokines, antibodies. The adaptive immune response is specific and develops memory.
The complement system
– comprises at least 9 plasma proteins & some regulatory factors, that mediate several
functions of the inflammatory process
– synthesised by macrophages or hepatocytes
– usually circulate as inactive proenzymes
, – heat labile at 56℃ (vs antibodies heat stable)
Complement activation
– Cascade of sequential activation converts each proenzyme C1 > C9 into its active state &
amplifies the response.
– Two main pathways:
“Classical” (indirect) pathway: bound IgG, IgM
“Alternative” (direct) pathway: certain antigens (LPS)
Functions of the complement system: chemotaxis, immune adherence, acceleration of acute
inflammation, immune cytolysis, bacterial killing / lysis, virus neutralisation
T-lymphocytes
• Th - CD4+: Respond to antigen in association with MHC Class II. CD4+ cells recognize antigens
that have been taken up by antigen presenting cells which present antigen fragments on the
cell surface
o Th-1 cells activate macrophages to destroy material phagocytosed and intracellular
organisms (“cellular immunity”)
o Th-2 cells help B-cells make antibody (“humoral immunity”)
• Tc - CD8+: Respond to antigen presented via MHC Class I. CD8+ cells recognise cells infected
with virus, which they then kill (CTLs)
For T cells the antigen must be a peptide, presented by APCs.
B-lymphocytes are specialised for the production of immunoglobulins after differentiation into
plasma cells IgM IgA, IgD, IgE, IgG, and can respond to peptide, carbohydrate & glycolipids. Usually
they require T-cell help to respond to antigen (interleukins) but can also recognise antigen directly
through surface Ig. B cells mature and proliferate in lymph nodes. B cells neutralise toxins, prevent
adhesion, neutralise virus, opsonise bacteria, activates complement.
Specific immunity is termed humoral when antibodies are involved in removing the antigen
(Th2). It is termed cell-mediated when T-cells & macrophages are involved (Th1).
Immunity after infection is termed active immunity (because the host has responded actively to the
stimulus). Immunity may be transferred passively by antibodies or cells: breast milk, maternal
antibodies, Post Exposure Treatment (Rabies, snake venom).
“Vaccination” may be passive (using Ig or cells) or active (using antigen or attenuated organism).
HC Sep 5. Basic Principles of infectious diseases
By the 1960s, with improved sanitation, medicine and drugs, the U.S. Surgeon General stated, "the
war against infectious diseases has been won." (antibiotics/vaccines/hygiene/nutrition)
But, the war continues today: The campaign to eradicate infectious disease is ongoing
Pathogens are exhibiting remarkable resilience and flexibility.
Infection: When a microorganism is present in a host in places where it is not normally found
(replicating). Infectious disease: When this causes illness.
Endemic disease: Disease constantly present in a population
Epidemic disease: Disease acquired by many hosts in a given area in a short time. Outbreak.
Pandemic disease: Worldwide epidemic.
, Cases
Index – the first case identified
Primary – the case that brings the infection into a population
Secondary – infected by a primary case
Tertiary – infected by a secondary case
Infectivity (ability to infect): (number infected / number susceptible) x 100
Pathogenicity (ability to cause disease): (number with clinical disease / number infected) x 100
Virulence (ability to cause death): (number of deaths / number with disease) x 100
Control: reduction of disease incidence, prevalence, mortality and morbidity
Elimination: reduction to zero of the incidence of infections caused by a specific agent
Eradication: permanent reduction of the incidence of infections worldwide
Public health surveillance: The systematic collection, analysis and interpretation of health data on
an ongoing basis and its timely distribution to those who need to know and subsequent use of the
data. Goal: to prevent or control the diseases within a population, by knowing and timely action.
HC Sep 12. Vaccination
Vaccination is one of the containment strategies (IHR). Vaccinations can be prophylactic, or used for
ring vaccination in case of an outbreak.
Vaccination is the simulation of an infection, aiming at the positive effect of stimulating protection
against a subsequent infection, while the negative effect is avoided as much as possible.
The first vaccinations were based on the observation that a person once recovered from an infection,
is mostly protected against re-infection. Variolation is infecting people with a mild form of the
disease. This started around 1000 AD in china, and came via India to Europe and America until in the
18th century. 5-10% of the people died after variolation.
Edward Jenner is the founding father of vaccination. In 1796 he started smallpox experiments in
people. Smallpox was then the most feared disease, and the cause of the disease (the virus) was
unknown. The mortality was 10% of the total population, increasing to 20% in cities. And it was
responsible for 30% of the child mortality.
Jenner chose the 8 year old son of his gardener and infected him with smallpox, six weeks after he
was vaccinated with cowpox. James appeared to be completely protected against smallpox.
Vaccination with cowpox became compulsory in England in 1853. In 1967 the WHO started an
intensive campaign to eradicate smallpox from the world. In 1977 a Somalian was the very last
patient who acquired smallpox naturally. In 1979 the world was declared free from smallpox.
It took many years from the discovery of the vaccine, until smallpox was eradicated, because people
feared vaccination. Some people still fear them nowadays. Smallpox and rabies had a vaccine even
before the viruses were identified. Since then, more and more vaccines were developed, with
different types of techniques:
– Live attenuated bacteria: BCG, oral typhoid (cannot be given to people with HIV)
– Inactive bacteria: whole cell pertussis
– Live attenuated viruses: measles, mumps, rubella, oral polio, influenza (easiest to produce,
relatively cheap, also strong immune response because they resemble the real virus.)
– Inactivated viruses: inactivated polio
– Polysaccharides: meningococcal, pneumococcal
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