Disease & Prevention

active immunity and example

protection produced by own immune system stimulated by a antibody and cell-mediated immunity

- provides long term protection

2 ways to acquire active immunity

1. via infection and recovery, if rexposed, the memory B cells begin to replicate and produce antibodies to reestablish protection

2. get vaxxed, which contain antigens that trigger the immune system to act (immune response)

what factors affect immune response? (4)

maternal antibodies, nature & dose of antigen, route of administration, presence of adjuvant (additives to improve immunogenicity of vaccine)

what are some host factors that affect the immune response? (4)

age, nutrition, genetics, comorbidity

What are live attenuated vaccines?

They are weakened but still active organisms (viruses) - a milder version but doesn't cause disease

e.g. MMR, rotavirus, smallpox, chickenpox, yellow fever

Inactivated vaccines

contains killed viruses/bacteria/pathogens that were cultured and killed to destroy their disease-causing capacity

e.g. pertussis, rabies, Hepatitis A, poliovirus

how does the immune system work

ability of human body to tolerate the presence of foreign material (bacteria, viruses, fungi) and to eliminate them

- develops defence against antigens via the production of protein molecules by B cells (antibodies) which are immunoglobulins and production of T lymphocytes

What do B cells produce? and for what?

antibodies (immunoglobulins) as an immune response

What is an example of a vaccination scheme?

at 3 months, 5 months, 11 months, 14 months, until 14 years etc. children would get certain vaccines throughout their lives

what is the purpose of a vaccination scheme?

eradicate conditions, decrease mortality rates (child)

What is herd immunity?

a large community becomes immune to a disease

what are key determinants of herd immunity?

reproduction number (R0) - expected number of cases generated by one case in a population where everyone is susceptible for an infection

what should the reproduction number be for the disease to be eradicated?

smaller than 1

what may affect the R0 number

heterogenous population (diverse), which are more interconnected will increase transmission and thus requires a larger vaccination threshold

what are freeloaders?

people who don't participate in vaccination for herd immunity and depend on others to achieve herd immunity

they will be very vulnerable for a focal outbreak around them

how can social media influence vaccination decisions?

by delivering info that changes perceived personal risk of vaccine preventable diseases or side effects

what would be a solution to have a better platform to provide information for vaccines

- implement interactive, customized communication

- increase effectiveness of existing communicatoin

- when there is less knowledge, need for reliable info on benefits & risks

What is Web 2.0?

Describes blogs, social networks, and internet-based services that emphasize collaboration and sharing

what are some web 2.0 challenges

for PH communication, online info influences people and everyone reacts to it, which makes it difficult to communicate safely (misinformation, etc.)

how do people get influenced easy on social media?

confirmation bias - they search for info that fits their beliefs rather than info that opposes their beliefs

how could the government have better communication?

- natural frequencies (statistic representation)

- visual support (infographics, videos9

- focus on facts and alternative explanations for myths

what are challenges in global immunization? (6)

- vaccines are not available to the poorest (inequality in distribution)

- false claims for associations for autism and vaccinations

- vaccines take a long process, expensive and difficult to make

- as more vaccines are added to the immunisation schedule, there is a need for more immunological interference when given together (a lot of research)

- confirmation bias

- vaccine hesitancy - delay in acceptance or refusal of vaccines despite the availability of them

what solutions are there for vaccine inequality?

better ways to target vulnerable communities with interventions

what are reasons for vaccine hesitancy (6)

- language barrier

- social media influences with false info

- cultural, religious beliefs

- politics

- gender

- trust in government or health system

what is TB?

infectious disease caused by a TB bacteria and attacks the lungs mostly

what is latent TB?

bacteria stays in body and is inactive, only activates when getting older and immune system suppresses + if comorbidities (esp. HIV/AIDS coinfection)

how is tb caused?

bacteria (Mb.), can survive in dry environment, only grows in living organism

- part of a family of bacteria

where can TB be detected as well? and how was the vaccine made (with what)

in cattle

the vaccine was made with the weakened living Mb. Bovis that causes TB in cattle

how does tb transmit

human to human, by coughing, sneezing etc. (airborne)

goes into alveoli in lungs

what is the primary infection of tb

immune system is battling the antigen locally (not yet spread further)

- no symptoms

what is the secondary infection of tb

latent tb, when it stays inactive

what is open tb?

when inflammation ruptures and gets into the airways and spreads into lungs

what is miliary tb

when inflammation ruptures and gets into the bloodstream and spreads throughout the body

what are symptoms of active tb

active --> fever, night sweats, weight loss, fatigue

in lung --> prolonged coughing, sputum, cough blood, chest pain, shortness of breath

how do you diagnose tb?

- case history (symptoms, traveling or born in prevalent country)

- physical exam (listening to abnormal sounds)

- lab & radiological investigation (interferon gamma test, skin test tuberculin, smear sputum, XpertMBT/RIF pcr test, x-ray)

what is the interferon gamma test

measures t cell response to the TB antigens and sees whether there is TB infection from BCG or actual infection

what is the skin test tuberculin (latent or active tb?)

for latent tb, inject tuberculin antigen (protein extract) into skin and if person develops a rash/swelling/redness after 2-3 days larger than 1cm, theyre positive for TB

- wont be positive in primary infection since the antibodies arent formed properly yet

what are drawbacks to the tuberculin skin test?

- if vaccinated, false positive would show since antibodies form vaccination formed (not infected with TB)

- if immune system is suppressed, (HIV/AIDS), false negative may come up (weak antibody production for anything)

what is the smear sputum? (latent or active?)

active, if antigen is high, red dots can be seen on a microscopic level

what was the old and new golden standard for tb testing?

(old) culture --> breeding/culturing the antigen in its ideal environment and testing what type it is and whether it is sensitive to treatments
- see what drugs work best, if sensitive it will not grow and drug can be used, however, very slow process

(new) pcr XpertMTB/RIF --> DNA is multipled and see if there is TB-bacterium DNA, detects resistance of rifampicin (most important drug for tb)
- very expensive but fast

what is the x-ray for tb? (latent or active?)

active, showing presence for active disease

what is the prolonged multi-drug treatment for tb?

combining drugs to prevent resistance too

what are the treatments for tb and mtb

- prolonged multi-drug

- chemoprophylaxis

- (MTB) antibiotics and chemotherapeutics (not related to chemo, just made in lab)

what is chemoprophylaxis for tb?

prevention of disease after exposure

- used in children after contact with contagious patient

how to treat active tb

2 month long with 4 drugs Isoniazide (I), Rifampicin (R), Ethambutol (E), Pyrazinamide (P)

decrease bacteria and limit contagiousness

then 4 months with 2 drugs (I) and (R)

downsides of treating active TB

lots of side effects --> hepatitis, nervous disorders, eye disorders

if comorbidity, alcohol or other drugs are used, need to be careful

what are the consequences if active TB treatment is not consistent? (6)

- development of resistance against drugs

- reactivation of TB

- complex and long process

- size of tablets

- further issues with comorbidities, addiction and low SES

- not cheap

what is a treatment for mtb?

antibiotics (organic origin) and chemotherapeutics (not linked to chemotherapy, just made in lab)

what are the risk factors for the activation of TB? (5)

- immune-suppressing conditions (HIV/AIDS)

- immune-suppresive drugs

- alcoholism

- diabetes, undernutrition

- genetic susceptibility

what are the risk factors for death from TB? (5)

- comorbidity

- accessibility of treatment

- resistance to drugs

What is MDR and XDR?

mdr - multidrug resistant tb (2 drugs)

xdr - extensively drug-resistant (almost every drug (4 drugs))

why are people developing mtb or even xdr?

- weak health systems

- inadequate treatment process (difficult to stay on track

- high transmission between communities

- unnecessary antibiotic provision for other infections

what happened after the collapse of the USSR? (MDR)

prevalence increased with weak health systems (fewer drugs, drugs are expensive)

why are elderly prevalent in TB?

because their immune system weakens once theyre old, and the latent infection that they had activates

where is mtb frequent?

Eastern Europe and Africa

what is the aim of surveillance of TB?

reduce burden of morbidity and mortality from TB via contact tracing (notifying when there are cases) and seeing trends & patterns

What is the vaccine for TB?

BCG vaccine

how effective is the BCG vaccine

not effective, but protection is reported in children and newborns

what are types of control for TB? (4)

surveillance

vaccination

screening

outbreak management

how would you usually screen for TB?

x-ray of thorax when coming from a region with high TB prevalence

then treat and supervise the case

what are 2 issues with the BCG vaccine and positive test results in tuberculin skin test?

1- if a vaccination was made, the test will come back positive - making it difficult to distinct and infection from the vaccine

2- false negative if the individual has a immune suppressive condition, the results will be negative, not showing how the body fights back

outbreak management in TB (stone-in-the-pond principle)

investigate contacts closest and longest contact with index-case (e.g. group, family) first

--> if then no. of infected is bigger than expected, expand to bigger circle via DNA fingerprinting to identify source of infection

What are EIDs/newly emerging infectious disease?

emerging infectious diseases, newly appeared in a population

what causes the spread of infections (moving)

- travelling for reasons such as work, tourism, leisure

what are zoonoses? and what factors cause it? (5)

- infectious disease spread from animals to humans

- farming, keeping domestic pets, hunting, camping, deforestation/habitat destruction

what are the 4 categories of EIDs? (ARND)

accidentally emerging infectious diseases

re-emerging infectious diseases

newly emerging infectious diseases

deliberately emerging infectious diseases

what is newly emerging infectious disease

one example

disease recognised in humans for the first time

e.g. COVID-19

what is accidentally emerging infectious disease

one example

disease created by humans unintentionally

e.g. vaccine derived polioviruses (over time changed into a wild or naturally occuring virus)

what is re-emerging infectious disease

one example

when a previously known disease has re-entered human population in new locations or in a resistant form

e.g. HIV/AIDS, TB

what is deliberately emerging infectious disease

one example

disease associated with the intent to harm (e.g. bioterrorism)

e.g. engineered microorganisms such as inserting genetic virulence to worsen a disease

what factors influence these infections? (3 categories)

host --> humans who are susceptible to those infections

agent --> susceptibility to an agent

environment

what are the environment factors for infections? (7)

- animal exposures

- traveling, commerce, tourism

- environmental degradation (urbanisation, deforestation, economic development, land use)

- climate & weather events

- poverty (lack of PH infrastructure, availability & accessibility, lack of surveillance & monitoring for infections)

- lack of political will (countries focus on different things)

- deliberate use of terror and harm

what are the objectives for surveillance? (4)

time - how are these disease trends, do they coincide with interventions? (e.g. vaccines)

place - where is the disease, geographic variations & factors

person - who is affected, minority groups, gender, age, culture, SES, race, occupation

disease characteristics - clinical or lab characteristics, severity and outcome

why is covid and ebola so different? they are two pandemics tho..

covid spreads really fast to others and mostly passes with light symptoms

whereas ebola also spreads fast but symptoms are severe and cause death so transmission is slower (since ppl are dying, they cant spread to anyone much)

what is risk assessment?

research and evaluation on effects of substances or practices --> gaining understanding of positive & negative effects

what is risk estimation

scientific judgement on past events to predict size and likelihood of future events and estimates of uncertainty

what is risk evaluation

relies on social & political judgement to determine importance of hazards and estimated risks

what is the process of risk communciation

estimate risk
evaluate risk

define options

make decisions

take action

monitor outcome

what needs to be considered for risk communication? (4)

- different stakeholders to get a broader perspective

- potential pitfalls

- consider target audience risk perceptions (including beliefs and cultural/religious contexts)

- be open and accept uncertainty (transparency)

- language of risk with clear and only useful info that everyone understands (building on existing info, verbal info is perceived better where numeric info is difficult)

who did a good and bad job in SARS control ?

Singapore restricted travel to contain

China did not restrict

Canada was slow in communication

British ministry denied risk of infection

what is a biased way of individuals thinking about risk estimation example

when there are news on high rates of accidents, individuals would think that they themselves wont be in that rate because they drive carefully

how do you achieve herd immunity?

only a part of the population needs to be immune to prevent huge outbreaks (when R is less than 1)

how do you achieve herd immunity with vaccination when infection rate is very high?

larger vaccination rates the larger the infections rate

what is CVD?

group of disorders of the heart and blood vessels

what is atherosclerosis

happens in coronary heart disease, when plaque (cholesterol deposits) builds up in the walls of the coronary arteries, they narrow over time

how do you diagnose CVD?

- ECG

- blood measures (cholesterol levels, blood pressure)

what are the 2 types of CVD tereatments?

pharmacological --> medication to control and reduce risk factors (statins, aspirin, surgery (bypass),

non-pharmacological --> lifestyle changes (smoking cessation, increase PA, limit alcohol, focus on healthy diet, stress, reduce obesity)

what are risk factors of CVD (12)

smoking
hypertension

obesity

unehalthy diet

limited PA

excessive alcohol consumption

family history & genetics of strokes

diabetes & metabolic syndromes

age

sex

chronic kidney disease

prior CVD experience

which age and sex group experiences hypertension more?

men 65 and older

how could primary and secondary prevention look like for CVD?

primary --> lifestyle change for people who experience risk factors

secondary --> prevent from further progression of CVD via medication and lifestyle changes

in which age group and sex has a higher CVD mortality rate ?

men have higher rate at 84 but for women it starts at 85-95 due to their longer life expectancy (the longer they live, the more CVD peaks) and menopause (estrogen decreases, risk of CVD increases)

what are risk prediction models?

estimate populations risk to develop CVD and to be able to control it in time with prevention strategies

to predict fatal and non fatal CVD

how does the prevalence looks like in CVD?

mortality and prevalence decrease lately

what do risk prediction models include? (7)

age, smoking, blood pressure, cholesterol, sex, diabetes, systolic blood pressure

what are cons of risk prediction models? (3)

most of them are not externally valid and are different in countries, some risk factors (e.g. diabetes) are missing

what are the 3 risk prediction models?

SCORE model

Framingham model

Q-risk model (up to 10 years in future)

what is preconception carrier screening (PCCS)?

investigating whether a genetic disorder is present in someone who is about to get pregnant (before pregnancy)

what is selective preconception care?

screening on request of the patient

what is premarital screening?

testing couples before getting married for genetic blood disorders and infectious diseases

what is universal preconception care

screening offered to populations from healthcare professionals