2b Epidemiology of Diseases of Public Health Significance Flashcards
Salmonellosis
C – Bacteria - Salmonella Enteritica
D – Endemic worldwide. 2nd most common UK bacterial diarrhoea (10,000/year), Children, October.
C – Diarrhoea (Sometimes bloody), N&V
I – Stool sample
I - 6-72 hours
I – While in stool (weeks/months),
M – FO
R – Animals e.g. Poultry
C - Hand hygiene, WHO Food handling, Pasteurised Foods, Stay home, Notifiable (food poisoning).
Shigellosis
C – Bacteria - Shigella sonnei
D – 160 million/year globally (most children). UK 2000/year (most travellers).
C – Diarrhoea (bloody/mucous)
I – 1-3 days
I – Stool Sample
I – Infectious while organism in the stool (weeks)
M – FO
R – Humans
C - Hand hygiene, Safe food, Stay home, Notifiable (food poisoning), Water sanitation.
Campylobacter
C – Bacteria - Campylobacter Jejuni
D – Most common UK bacterial diarrhoea (50,000/year), Spring/summer, Travellers, Children ( proportion of adults is rising).
C – Prodromal illness with fever, then Bloody diarrhoea, N&V, lasts 1 week.
I – Stool sample
I – Throughout infection
I – 2-5 days
M – FO, Contaminated Food
R – Humans, Animals
C – Hand hygiene, WHO Safe food 5 steps, Stay home, Antibiotics for certain cases (reduces infective period), Notifiable (food poisoning).
Listeriosis
C – Bacteria - Listeria Monocytogenes
D – UK 200 cases/year. 15% pregnant women.
C – Diarrhoea, N&V, Fever, Risk of miscarriage if pregnant
I – Blood culture
I – 1-90 days
I – While bacteria in stool (up to months)
M – FO, Vertical, Contaminated Food (soft cheese, unpasteurized milk, smoked fish)
R – Animals, Soil
C - Hand hygiene, WHO Safe food 5 steps, Stay home, Notifiable (food poisoning).
Cryptosporidiosis
C – Parasite - Cryptosporidium
D – Endemic in developing countries. UK 4000/year, HIV, Children.
C – Sudden onset watery diarrhoea, N&V, and Cramps which last for 1-2 weeks.
I – 2-10 days
I - While organism in the stool (weeks)
I – Stool sample for oocytes
M – FO, Infected water sources (crypto is resistant to chlorine)
R – Humans, animals
C - Hand hygiene, WHO Safe food 5 steps, Stay home, Notifiable (food poisoning).
E coli 0157
C – E. coli bacteria. Multiple strains, The Most severe is Shiga toxin E. coli (STEC) with the most common subtype of this being E.coli 0157.
D – UK 500 cases/year, Children, Rural areas.
C – Bloody diarrhoea. 30% hospitalised. 10% risk of thrombotic thrombocytopenic purpura (TTP) or haemolytic uraemic syndrome (Renal failure, anaemia, thrombocytopenia - 5% mortality rate).
I – 2-10 days
I – While excreting pathogen (Normally 1 week, but can be longer)
I – Stool sample
M – FO, Infected food
R – Animals (Cattle)
C - Hand hygiene, WHO Safe food 5 steps, Stay home, Notifiable (food poisoning). HUS is notifiable. Safe farming practices e.g. irradiating foods.
Typhoid
C – Bacteria - Salmonella enterica typhi/paratyphi
D – Endemic in developing countries (poor sanitation, unsafe drinking water, flooding and poor sewage systems - 20 million cases per year). Low levels in the developed world. UK rates falling since 2010 (200/year). High risk when travelling in south-east asia.
C - Fever, anorexia, headache, constipation or diarrhoea, rose-coloured spots on the chest area, hepatosplenomegaly. Typhoid more severe and lasts longer. Mortality normally <1% however in emergencies e.g. War, Flooding, up to 30% (even with antibiotics).
I – Stool sample
I – 1-3 weeks
I – While in the stool (5% become chronic carriers)
M – FO, Shellfish high risk
R - Humans
C – Immunisation for some overseas travel, Hand hygiene, WHO Safe food 5 steps, Stay home, Notifiable (food poisoning).
Cholera
C – Bacteria - Vibrio cholerae, serogroups 01 and 0139
D - Endemic in developing countries due to poor sanitation, unsafe drinking water, flooding and poor sewage systems (2 million cases per year). 7 major pandemics in the last 200 years. Rare in the UK, 10 cases/year from imported cholera. Risk to international travellers is low
C – N&V, Diarrhoea (10% of cases sudden onset/profuse), Dehydration. Severe cases 50% mortality if untreated (1% with treatment).
I – Stool sample
I – 1-5 days
I – During diarrhoea and 7 days after
M – FO, Seafood common
R - Humans
C - Hand hygiene, Safe food, Stay home, Notifiable (food poisoning).
Meningococcal Meningitis
C – Bacteria - Neisseria meningitidis – Common serogroups A, B, C, Y and W135. The most common in the UK is B.
D – Endemic worldwide, Meningitis Belt in sub-Saharan Africa (ACWY) with annual cycles and periodical large-scale epidemics. 1500 cases a year in England (common in under 5’s and 15-20’s). More common in winter. Most cases are sporadic but some outbreaks at schools/universities.
C – Adults (Meningitis, septicaemia) Children (floppy, irritability, fever). Meningococcal septicaemia (purpuric non-blanching rash). UK Fatality rate 10% (worsens with age). 10-20% develop permanent sequelae (hearing loss, brain damage etc).
I – Culutre of CSF
I – 2-10 days
I –While producing live meningitis vaccine from nose/mouth, 10% of asymptomatic carriers. Most people are no longer infective within 24 hours of abx.
M – Droplet spread via nasopharyngeal secretions
R - Humans
c – Treat with abx, Men ACWY Vaccine, Chemoprophylaxis of contacts (even for vaccinated). This includes those who lived with them within 7 days of symptoms). Immunisation of contacts if due to a vaccine-preventable strain and unvaccinated. Notifiable disease.
Haemophilus Meningitis
C – Bacteria - Haemophilus Influenza Type B
D – Common in children <3 years. Prior to immunisation, HiB was the second most common cause of bacterial meningitis in the UK. Now 150 cases per year.
C – A range of infections – Meningitis (60% of cases - 5% mortality, 30% sequelae rate). Other infections include pneumonia, epiglottitis, and bone and joint infections.
I – CSF culture.
I - 2-4 days
I - As long as organisms are present. Most people are no longer infective within 48 hours of abx.
M - Person to person, transmitted by droplet aerosol or secretions from the nasopharynx of colonized persons.
R – Humans
C – Vaccination, Notifiable disease.
Pneumococcal Pneumonia
C - Bacteria - Streptococcus pneumoniae
D - UK 5000 cases/year. Children, Elderly, immunosuppressed, Asplenic, Winter
C – Pneumonia (other infections include middle ear infection and meningitis).
I – Sputum culture, Xray
I – 1-3 days
I – Unknown communicability
M – Direct contact with respiratory secretions
R – Humans nasopharynx
C – Vaccination offered to newborns, those over 65, and high-risk.
Legionnaires disease
C - Bacteria - Legionella pneumophilia
D – UK 300 cases/year, 50% contracted abroad, Accounts for 10% of community pneumonias, Diabetics, Elderly, Immunocompromised, Chronic lung disease, alcohol, smokers.
C – Pneumonia, anorexia, malaise, myalgia, headache and fever, 10% mortality rate .
I – Sputum sample
I – 2-10 days
I – No person top person spread
M – Inhalation of contaminated aerosols e.g. Aircon, Jacuzzi
R – Water (chlorine resistant),
C - Appropriate design, maintenance and monitoring of water systems including disinfection of pools/spas. Use of sterile water for respiratory therapy devices. Notifiable disease.
Tuberculosis
C – Bacteria - Mycobacterium tuberculosis
D - One of the leading causes of infectious deaths worldwide (10 million cases/year). 80% in sub-Saharan Africa and Asia. Rates rising due to HIV, neglect of TB control programs, poverty and immigration. UK 4000 cases/year. Rates fell until the 1980s and then rose, highest prevalence London, Black African ethnicity. Those born in high prevalence countries born abroad. Risk factors (immunosuppressed, alcohol, drug users, diabetics, and malnutrition).
C –30% of people exposed develop active or latent disease (50/50). 10% of latent cases develop active TB at some point. Risk of reactivation increases with age, chronic disease and immunosuppression (The leading cause of death in HIV). 70% of UK cases are pulmonary TB. Symptoms include (Fever, Night sweats, cough, and weight loss).
I – Active (Xray, Sputum sample), Latent (Mantoux test or IGRAS)
I – Active (3-12 weeks) Latent (years)
I – While bacteria in sputum (2 weeks after treatment start)
M – Person-to-person spread via droplet transmission, Less commonly ingestion of infected animal material e.g. Unpaterised milk
R – Humans, Cattle
C – Notifiable disease, Vaccine for children in high prevalence areas or whose parents come from high-risk TB countries, healthcare workers.
Hepatitis A
C – Hepatitis A Virus
D - Endemic worldwide (160 million cases/year), Developing countries have higher incidence and most people have it as children, in developed countries most get it as adults. UK 700 cases/year, rates declining over time.
C – Asymptomatic, Fever, Abdo pain, Anorexia, N&V, diarrhoea, Dark urine and jaundice. 15% of infected individuals will have prolonged illness or relapsing symptoms over 6 months. 0.6% mortality (higher in older adults). Infection results in lifelong immunity. No chronic infection occurs.
I – Blood test for IgM antibodies for HAV
I – 15-50 days
I – 2 weeks before the onset of symptoms to 1 week after
M – Faecal oral (e.g. Shellfish), Blood exposure (rare)
R - Humans
C – Vaccination for travellers to high endemicity countries, Handwashing, Safe food prep. Isolation until 7 days after jaundice. Notifiable disease
Hepatitis B
C - Hepatitis B Virus
D – Endemic worldwide (1 million deaths/year, 350 million chronic carriers, 10% carrier rate in some countries). UK - 300 cases/year, most infections horizontal transmission in early adult life (sexual contact, IVDU).
C – Range from asymptomatic to fulminant hepatitis ( fatigue, abdominal pain, anorexia, N&V, jaundice). Rate of chronic HBV infection is age-dependent (Around 10% but younger is higher).
Chronic infection occurs in approximately 90% of infants infected at birth, between 30% - 50% of children infected at age 1-5 years and among 10% of adults.
The risk of death from HBV related liver cancer or cirrhosis is approximately 25% for persons who become chronically infected during childhood.
I – Serological blood testing
I 45-180 days
I Any infected individual is infectious
M – Boldily fluids, Horizontal in UK, Vertical in Asia/Africa
R - Humans
C - Provide advice and immunization to overseas travellers, HBV prophylaxis for reported exposure incidents, vaccines offered to newborns and high risk patients. Notifiable disease.
Hepatitis C
C – Hepatitis C virus
D – Endemic worldwide, 130 million chronic carriers globally, WHO target to eliminate 90% of cases by 2030. UK 0.5% prevalence, 90% IVDU, Young adult men.
C – 90% of cases are asymptomatic, symptomatic cases include anorexia, fever, jaundice, and abdominal pain. 80% develop chronic infection of which 25% develop cirrhosis. 4% of cirrhosis cases develop HCC.
I - Anti-HCV IgG antibody tests are normally positive within 3 months of infection
I – 2-6 weeks
I – For 1 week before symptoms and then ongoing
M – Bodily fluids
R - Humans
C – Treat with antivirals, reduce risk factors. Notifiable disease.
Diphtheria
C – Bacteria - Corynebacterium diphtheriae
D – Endemic worldwide, 10 cases per year in England, Recent UK outbreaks in asylum seeker populations (80 cases in 2022).
C – Symptoms range from a moderately sore throat to toxic life-threatening diphtheria of the larynx or of the lower and upper respiratory tracts. Cutaneous infection causes sores.
I – PCR blood test for diphtheria toxin
I – 2-5 days
I - Untreated cases remain infectious for up to 4 weeks, after 3 days of antibiotic treatment cases are no longer infectious
M - Airborne droplets or direct contact with infected respiratory discharges or skin ulcers.
R – Humans
C – Childhood vaccine programme, Treat with anti-toxin and antibiotics, Antibiotics for close contacts, Contacts get booster shot if not up to date with vaccines. Notifiable disease.
Pertussis
C – Bacteria - Bordetella pertussis.
D –Endemic worldwide (50 million cases/year). Major cause of childhood mortality in developing countries . UK 500 cases/year.
C – 3 stages In adults symptoms range from mild respiratory infection to paroxysmal cough episodes. Severe infections in infants (50% hospitalized). Complications in infants include pneumonia seizure, encephalopathy, and death). Infection can occur in immunized and previously infected individuals, but both reduce the seriousness of infection.
I – Nasopharyngeal swab culture.
I – 6-20 days
I - Highly infectious during the first 4 weeks. Not infectious 5 days after antibiotic treatment.
M – Droplet
R - Humans
C – Treat with erythromycin. Childhood immunisation, Isolation until after 5 days of treatment, Vaccination of unvaccinated household contacts and exclusion from school etc, Antibiotic prophylaxis may be of value for unvaccinated household contacts of cases. Notifiable disease
Tetanus
C - Clostridium tetani.
D – Present in the environment worldwide, 300,000 deaths worldwide each year (mainly in Africa/Asia). 5 cases per year in the UK following vaccination.
C - rigidity and convulsive spasms of skeletal muscles. Mortality 10-80% (worse in infants and elderly)
I – Clinical diagnosis
I – 3-21 days
I – No person-to-person transmission
M – Puncture wounds with contaminated material
R – GI tract of humans and animals, Spores found in animal faeces or soil.
C – Vaccination programme. Booster following high-risk injuries if not up to date. Notifiable disease.
Polio
C – Poliovirus types 1,2,3. Type 1 most common.
D – 99% case reduction following 1988 WHO Global Polio Eradication Initiative. Globally 2000 cases/year (Children, Africa, Asia). No UK cases in 20 years.
C- Most cases are asymptomatic. 10% minor, non-specific illness. 5% aseptic meningitis. 1% flaccid paralysis (paralytic polio). 5% mortality from paralytic polio in children (higher in adults).
I – Throat swab, stool sample, CSF sample
I - 3-35 days
I – Highly infectious (100% seroconversion in households), Humans are infectious 10 days before symptoms and up to 6 weeks after.
M – Faecal oral
R - Humans
C – Immunisation (now we use inactivated vaccines to reduce the risk of vaccine-derived polio), Notifiable disease.
Mumps
C – Mumps virus
D – UK - Falling levels since 1987 MMR Vaccine. Recent outbreaks (5000 cases in 2019 ) following 2004 MMR scandal - Most cases unvaccinated uni students). Prior to vaccine outbreaks occured 3 yearly.
C - Acute viral illness characterized by fever, headache, tenderness and swelling in one or both parotid salivary glands. Asymptomatic in 30% children. Complications rare (aseptic meningitis, orchitis in 25% of adults)
I – Serology of saliva, blood, urine or CSF.
I – 14-25
I - 7 days before to 9 days after the onset of parotid swelling
M – Airborne, Droplet
R - Humans
C – MMR Vaccine (1 and 3 years), Exclusion from school for 5 days from onset of parotid swelling. Notifiable Disease
Measles
C – Measles Virus
D – Endemic worldwide (the leading cause of death in young children - 500,000 deaths per year and the leading cause of blindness among African children). 1998 MMR Vaccine reduced UK rates, which rose again following the 2004 Wakefield MMR scandal (1000 cases 2018).
C - Prodromal illness with fever, coryza, respiratory infection, conjunctivitis and Koplik’s spots in the mouth. Rash on the 3-7th day, initially on the face then generalized lasting 4-7 days. 20% complications including otitis media, pneumonia, corneal scarring, croup, diarrhoea and encephalitis. 5% mortality rate (30% in vulnerable). Risk of spontaneous abortion, premature labour and low birth weight in pregnancy.
I – Serology of oral fluid/blood
I – 10-12 days
I - 1 day before the prodromal period until 4 days after the rash appears.
M - Droplet infection or direct contact with nose and throat secretions (most non-immune children exposed become infected).
R - Humans
C – MMR Vaccine (1 and 3 years), School exclusion until 4 days from onset of rash. Notifiable Disease
Rubella
C – Rubella Virus
D – Global (100,000 cases of congenital rubella syndrome each year). UK - No cases since 2019, Prior to the vaccine, epidemics occurred in 6-year cycles peaking during winter/spring.
C - Mild viral illness with swollen lymph glands followed by maculopapular rash 3 days later. Children may be asymptomatic. Intrauterine transmission in the first trimester is >90%, 50% in the second trimester (no increased risk >20 weeks). May result in miscarriage, stillbirth or congenital rubella syndrome (low birth weight, cataracts, heart defects, hearing impairment, small head size and developmental delay)
I - Laboratory diagnosis by oral fluid testing
I – 14-21 days
I - From 1 week before the onset of rash to 1 week after the onset of rash.
M – Airborne transmission or droplet spread
R - Humans
C - MMR Vaccine (1 and 3 years), Screen in early pregnancy and immunize post-partum, School exclusion 4 days from onset of rash. Notifiable Disease.
Chlamydia
C – Bacteria - Chlamydia trachomatis.
D – Globally - 130 million cases/year, UK most common STI (200,000 cases/year). 16-20 females and 20-24 men, Low SES, Multiple sexual partners.
C – Women (70% asymptomatic, urethritis, cervicitis – Discharge, dysuria, blood/pain in sex). Men (50% asymptomatic, urethritis, epididymitis – Discharge, Dysuria) Complications in women (Pelvic inflammatory disease, infertility, ectopic). Untreated infection increases the risk of HIV. Can also infect other areas e.g. Rectum or Eye (The leading cause of blindness in the developing world).
I – Vaginal swab
I – 7-14 days
I – Until treated
M – Sexual contact, Vertical
R - Humans
C – 7 days of antibiotics, abstain from sex until treatment is complete, Safe sex practices, Patient-led partner notification, Proactive primary care screening offered to young women.
