What do you need to do to stop an infection?
need to remove any element of the chain of infection to prevent a susceptible host acquiring an infection
What is the agent in influenza?
Orthomyoxviridase (RNA viruses) - types A, B, C
Classical respiration/systemic illness, complications frequent
What is the epidemiology of influenza?
Winter epidemics in temperate regions
3-30K excess deaths in the UK
What is the reservoir for influenza?
human, pig, avian
Who is susceptible to influenza?
Universal until immunity acquired to specific subtype
What is the incubation and period of communicability for influenza?
Incubation: 7-67 hours (median is 34 for type A)
Highly infectious for 1 day before symptoms to 1-2 days after (very low after 7 days)
What are the means of preventing/treating of influenza within its chain of infection?
1) Infectious agent: Rapid diagnosis and identification
2) Reservoir: Immunisation, specific anti-viral meds
3) Portal of exit: Respiratory hygiene
4) Mode of transmission: Isolation, hand washing, respiratory hygiene, environmental cleaning
5) Portal of entry: Infection control - Personal protective equipment (PPE)
6) Susceptible host: Immunisation, antiviral chemoprophylaxis, public health management of outbreaks
What are the different modes of transmission?
Direct = directly from reservoir to host
- contact with skin/mucous membrane/blood or other bodily fluids
- droplet spread (respiratory route)
- transfer of faecal contamination to mouth (faecal oral route)
Indirect
- Vehicle borne- inanimate material or object (fomites), contaminated food or water (faecal oral route), contaminated sharps (blood borne route)
- Vector borne-mechanical or biological
Airborne
- dissemination of microbiological aerosols (<5micrometers)
What is different about measles compared to flu?
Measles is an entirely human condition
What is the agent for measles?
Paramyxovirus (RNA virus)
Rash and systemic illness, significant complications occur
What is the epidemiology for measles?
Now rare in developed countries
What is the reservoir for measles?
Human only
Who is susceptible to measles?
Universal until immunity acquired
What are the modes of transmission for measles?
Direct contact with respiratory secretions/droplets
What is the incubation and period of communicability fo measles?
Incubation 7-18 days (typically 1 day)
Highly infectious just before rash and for 4 days after
What are the means of preventing/treating of measles within its chain of infection?
1) Infectious agent: rapid diagnosis and reporting
2) Reservoir: Immunisation, healthcare employment screening
3) Portal of exit: respiratory hygiene
4) Modes of transmission: isolation, hand washing, respiratory hygiene
5) Portal of entry: Infection control PPE
6) Susceptible host: Immunisation, immunoglobin, public health management of outbreak
What is the “green book” from PHE?
Schedule for vaccine preventable infections -changes over time
What are our routine childhood immunisation programmes?
- Diptheria, tetanus, pertussis, influenza B, pneumococcal, rotavirus, men C, men B, measles, mumps, rubella, influenza
What are our routine adulthood immunisation programmes?
HPV, tetanus, diphtheria, polio, men A,C,W,Y
What are some other immunisation programmes?
flu, pneumococcal, shingles
What are the selective immunisation programmes?
Hep B -babies born to infected mothers
BCG -high prevalence areas or family link to high prevalence countries
Influenza - pregnant women
Pertussis - pregnant women
What are the immunisation programmes for individuals with underlying medical conditions?
Splenic dysfunction or complement disorders - men A, B, C W, Y, pneumococcal, Hib, influenza)
Cochlear implants - pneumococcal
Diabetes and chronic respiratory/cardiovascular/neurologial disease - pneumococcal, influenza
Chronic kidney disease - pneumococcal, influenza, hep B
Chronic liver disease - Pneumococcal, influenza, hep A and hep B
Immunosuppression - pneumococcal, influenza
haemophilia - hep A and B
What is the agent for HIV?
Rotavirus, HIV 1 and HIV2
Acute seroconversion illness, progressing to AIDS if left untreated
What is the epidemiology for HIV?
variable according to risk groups (related to transmission) - increasing
What is the reservoir for HIV?
human only
Who is susceptible to HIV?
Universal
What are the modes of transmission for HIV?
via exposure to blood, issues, semen, mucous membranes
vertical transmission
What is the incubation and period of communicability for HIV?
Nucleic acid sequences detectable 1-4 weeks after exposure
infectivity relates to viral load and co-morbidity
What are the means of preventing/treating of HIV within its chain of infection?
Infectious agent / Reservoir: active case finding, specific antiviral meds, treatment of other STIs
Portal of exit: screening of blood and organ donation
Mode of transmission: Safer sex practice, harm minimisation approaches for injecting drug use, antenatal screening programme
Susceptible host: post-exposure, pre-exposure prophylaxis (PrEP), treatment of other STIs
What is the agent for salmonellae (non-typhoid)?
Salmonella enterica subspecies/serovars
Gastroenteritis (severe), systemic illness, extra-intestinal complications
What is the epidemiology for salmonellae (non-typhoid)?
common worldwide
What is the reservoir for salmonellae (non-typhoid)?
Many animals can be infected or acts as carriers
Who is susceptible to salmonellae (non-typhoid)?
Universal (partial immunity to related servers may be acquired)
What is the mode of transmission for salmonellae (non-typhoid)?
Ingestion of the organism
What is the incubation and period of communicability for salmonellae (non-typhoid)?
Incubation 4 hours to 5 days (typically 12-48 hours)
Infective dose 10to power of 3 - 10 to the power of 5
What are the means of preventing/treating of salmonellae enteritis within its chain of infection?
1) Infectious agent: rapid diagnosis and identification
2) Reservoir: immunising egg laying flocks, good practice in animal husbandry, abattoir and food chain occupation, good health practice
3) Mode of transmission: good practice in food prep and handling, isolation of cases, excursion of cases, enteric infection control precautions
4) susceptible host: public health management of outbreaks
What are the stages of statutory notification of infectious disease?
1) surveillance system
2) Legal duty for ‘registered medical practitioners’
3) Statutory basis for notification
4) Registered medical practitioners requirements
What is involved in the surveillance system?
- identify outbreaks
- evaluate current control measures
- provide info to plan health services
- identify changes to epidemiology/risk group
- trigger for local public health action
What acts are involved in the statuary basis for notification?
Health protection regulation 2010
Public health act 1984
Primary purpose - to enable the prompt investigation, risk assessment, and response to cases of infectious diseases
What are the responsibilities of registered medical practitioners?
“notifiy the proper officer of the local authority in which the patient resides when they have reasonable grounds for suscepting that the patient has…”
- notifiable disease
- an infection that (could) present significant harm to human health
- contaminated in a manner that could present signifiant harm to human health
What are the common / occasional / unusual / rare notifications for infectious diseases?
Common
- food poisoning, TB, mumps, scarlet fever
Occasional
- measles, whooping cough
Unusual
- Acute infectious hepatitis, Typhoid and paratyphoid fever, rubella, meningitis and meningococcal septicaemia
Rare
- tetanus, polio, cholera, rabies, viral harmorrhagic fever
What is the agent for hepatitis A?
picomavirus (RNA)
Wide range - from asymptomatic to fulminant hepatitis
What is the epidemiology for hepatitis A?
Decreasing in developed countries, common elsewhere
What is the reservoir for hepatitis A?
Humans
Who is susceptible for hepatitis A?
universal until immunity is acquired
What is the mode of transmission for hepatitis A?
Faecal oral route (ingestion), sexual and percutaneous transmission reported
What is the incubation and period of communicability for hepatitis A?
Incubation 15-50 days (mean 28 days)
Infectious from 2 weeks before symptoms to 1 week after adults
What are the means of preventing/treating of hepatitis A within its chain of infection?
1) Infectious agents: rapid diagnosis and reporting
2) Reservoir: Appropriate sewerage and sanitation facilities, water treatment processes
3) Modes of transmission: isolation of cases, exclusion of cases, enteric infection control, good practice in food handling and prep, safer sex, reduction in IV drug use
4) Susceptible host: Immunisation (occupation, travel, vulnerable cases), post exposure prophylaxis, public health management of outbreaks
What is hepatitis A like in <5year olds?
generally asymptomatic
What are the elements of the epidemiological framework?
Host- susceptibility, likelihood of exposure, response to agent
Agent- infectivity, pathogenicity, virulence
Environment - extrinsic factors affecting the agent and likelihood of exposure (social life, social behaviours)
In terms of the host, what helps to ensure they are safe, more likely to suffer and more likely to suffer severely from Hepatitis A?
Safe- past infection, immunisation
More likely to suffer- Travel, IV drug use, sex, occupation
More severe suffering- immune status, liver disease, older age
What are the severe symptoms of E. coli O157?
mild diarrhoea to severe haemorrhage colitis (related to age)
haemolytic uraemia syndrome
serious complications in up to 10% - case fatality 1-5%
What is the infective dose of E. coli O157?
Excretion continues for up to a week (longer in young children)
Incubation period typically 3-4 days (range from 2 -10 days)- very easy to catch
Where does E.Coli O157 live?
Cattle (<1% to 16%), sheep, deer, goats (also wild rabbits, pets and birds)
What are the modes of transmission of E.Coli O157?
Many routes of transmission
- inadequately cooked meat, cross contamination
Direct contact with animals - poor animal husbandry, inadequate hand washing
Environmental- water, farmland, manure used for vegetables, salad, fruit
What is the agent for E.Coli O157?
Gram -ve enterococcus