Covid-19 Epidemiology and Implications for Infection
This slide-deck covers basic epidemiology, clinical symptoms, and control measures related to Covid-19, including details on the virus, transmission, and testing as of June 30, 2020.
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Presentation Transcript
Covid-19 Epidemiology and implications for infection, prevention & control With thanks to everyone for sharing the materials that make up this slide-deck: Doncaster, Barnsley, East Riding & Leeds Public Health & IPC Teams Leeds Community Healthcare IPC team Sheffield Community Contact Tracers Sexual Health Team at DBTH
Structure Basic epidemiology Implications for infection, prevention & control Testing 2 Information as at 30.6.20
Before we start: timeline Cluster of cases of pneumonia of unknown cause Initial contain stage involved testing, contact tracing, active surveillance and quarantining. Identified as a novel coronavirus A PHE blog from this stage provides some of the detail and information about how contact tracing was carried out: https://publichealthmatters.blog.gov.uk/ 2020/02/13/expert-interview-what-is- contact-tracing/ Virus = SARS-CoV-2 Associated disease = COVID- 19 First UK cases late January Adapted from Doncaster PH team 3 Information as at 30.6.20
Basic epidemiology: what we know (and what we dont) Agent Clinical Symptoms Epidemiology (time/place/person) Diagnosis (will cover case definition, testing is in last section) Reservoir (we ll skip this all we need to know is human-to-human transmission is happening) Transmission Surveillance (notifiable disease, surveillance changing rapidly) Control measures (we ll do this in more detail in the IPC section) Adapted from Doncaster PH team 4 Information as at 30.6.20
Basic epidemiology: Agent A novel coronavirus Coronavirus is named for the crown-like spike proteins on the virus surface family of viruses (includes the viruses that cause MERS and SARS) SARS-CoV-2 novel virus first identified in Wuhan Dec 2019 Causes disease called COVID-19 Adapted from Doncaster PH team 5 Information as at 30.6.20
Basic epidemiology: Clinical symptoms New, continuous cough High temperature Loss or change to sense of smell or taste Adapted from Barnsley PH team 6 Information as at 30.6.20
Basic epidemiology: more severe infection Most people who get Covid-19 have a mild illness However for some it can be serious and there is growing evidence of longer- term consequences of more severe course of infection Clinical support needs to be provided by the NHS if conversations stray in this direction, we must encourage people to seek appropriate help Our joint role (PHE and Local Authority & partners) in this context is contact tracing, providing advice on isolation, ensuring people get tested and that they have support in place to self-isolate Click to see Chris Whitty s lecture, which has a section (about 55 minutes in) on more severe course of disease 7 Information as at 30.6.20
Basic epidemiology: cases, clusters & outbreaks Case definition: Positive test for COVID-19 with or without symptoms Cluster: Two or more confirmed cases of COVID-19 among individuals associated with a specific setting with onset dates within 14 days Outbreak: Two or more confirmed cases of COVID-19 among individuals associated with a specific setting with onset dates within 14 days AND Contact between at least two of the confirmed cases in that setting More on both of these in the other training packages, key things to remember are the 3 Rs: Recognition of outbreak in staff and patients Reporting Responding 8 Information as at 30.6.20
Basic epidemiology: time / place / person time Incubation period: currently estimated to be 1-14 days (avg 5) Length of illness: current reports suggest c.2weeks for milder cases and 3-6 weeks for severe Infectious period: Currently estimated to begin around 2 days before onset of symptoms and last until c.7 days after onset of symptoms. If a person still has a fever after 7 days, they should be considered potentially infectious and continue to self-isolate until this has resolved* *see https://www.gov.uk/government/publications/covid-19-stay-at-home-guidance/stay-at-home-guidance-for-households- with-possible-coronavirus-covid-19-infection for detailed guidance on ending self-isolation Adapted from Doncaster PH team 9 Information as at 30.6.20
Basic epidemiology: time / place / person place Confined spaces: settings where people can t physically distance (households, care homes, factory lines, vehicles) Settings where there are people who are more susceptible Crowded gatherings: settings involving more people Settings where people who are ill are cared for or live Adapted from Doncaster PH team 10 Information as at 30.6.20
Basic epidemiology: time / place / person person Vulnerable groups, including shielded (we think more at risk of severe illness, possibly more at risk of getting ill) Occupation (e.g. health & care workers) Other people who can t physically distance Adapted from Doncaster PH team 11 Information as at 30.6.20
Basic epidemiology: time / place / person person Are we all in the same boat? Adapted from Barnsley PH team 12 Information as at 30.6.20
Basic epidemiology: transmission (catching it and spreading it) At the moment, we think the primary modes of At the moment, we think the primary modes of transmission are: transmission are: Droplet Contact Not Covid-specific, but there are lots of animations and experiments showing how easily pathogens can spread, e.g. https://www.youtube.com/watch?v=I5-dI74zxPg and https://www.youtube.com/watch?v=1Pc0777SOqs Adapted from Doncaster PH team 13 Information as at 30.6.20
Basic epidemiology: control measures Related to transmission mode Whilst we wait for vaccine or treatment, focus on: Interrupting transmission and reducing contact between people Increasing healthcare facilities ability to support people who are ill Ensuring people can stay well at home (more likely to comply) Adapted from Doncaster PH team 14 Information as at 30.6.20
Basic epidemiology: control measures Kill the virus Protect more vulnerable Stop the spread Physical distancing Correct use of PPE Face coverings COVID-secure workplaces Self-isolation if symptomatic Test and Trace Handwashing Cleaning, disinfecting and decontaminating surfaces Shielding Adapted from Barnsley PH team 15 Information as at 30.6.20
Basic epidemiology: what dont we know (yet)? Infectious dose is unknown Immunity we don t know whether people develop immunity, who develops it or for how long this might last* Asymptomatic transmission we don t know much about this: are people with asymptomatic illness less infectious? Do they pass on a less severe illness** Series interval (time between one person being symptomatic and passing infection to another and them becoming symptomatic) Infection fatality rate Adapted from Doncaster PH team 16 Information as at 30.6.20
Basic epidemiology: quick re-cap Main symptoms: cough, fever, loss +/ change of smell +/ taste Isolation advice for cases and contacts relates to incubation and infectious periods We need to consider higher risk settings and people We think SARS-CoV-2 is primarily spread through droplet and contact Control measures are related to these modes of transmission Case-finding and testing*, contact tracing*, isolating and monitoring are bread and butter of infectious disease control and asymptomatic and pre- symptomatic spread makes them particularly important in this pandemic *covered a bit later and in other sections 17 Information as at 30.6.20
Structure Basic epidemiology Implications for infection, prevention & control Testing 18 Information as at 30.6.20
Implications for IPC: breaking the chain Adapted from Leeds Community Health Care 19 Information as at 30.6.20
Implications for IPC: physical distancing Adapted from East Riding IPC & PH team 20 Information as at 30.6.20
Implications for IPC: hand hygiene The single most important measure for preventing the spread of infection Gloves don t replace the need for hand-washing E.g. Gloves Are Off campaign from GOSH Adapted from East Riding IPC & PH team 21 Information as at 30.6.20
Implications for IPC: Frequently touched areas Placeholder Clean and disinfect all shared equipment. Where possible, reduce the number of people using each item of equipment Adapted from East Riding IPC & PH team 22 Information as at 30.6.20
Implications for IPC: Infection Control and Cleanliness Are cleaning roles and responsibilities clear? It is EVERYONE S JOB to clean as they go. Is there a robust cleaning schedule in place for the environment and patient equipment? Good old elbow grease - without cleaning an item first, it may not be possible to disinfect properly. The definition of cleaning in its simplest term is the removal of unwanted material without damaging the surface to which it adheres . In a healthcare environment, unwanted material includes dust, debris, marks and spillages, as well as microorganisms that can harm patients. The environment therefore needs to be visibly clean, as well as clinically clean: i.e. meeting safe standards appropriate to the (health)care setting. Adapted from Leeds Community Health Care 23 Information as at 30.6.20
Structure Basic epidemiology Implications for infection, prevention & control Testing 24 Information as at 30.6.20
Testing No test is 100% accurate Testing 101 = always think about the purpose of the test and what you will do with the result before you use it Reasons for testing could include: Improving general understanding (research / surveillance) If it will change how you care for people It will change the advice you give them (e.g. isolation) It could help reduce transmission (e.g. through more appropriate isolation) 25 Information as at 30.6.20
Testing: types of test antigen The antigen test detects the presence of virus in your system at a point in time +ve test result = usually accurate* However, may test positive but no longer be infectious Negative result may be false negative -ve test result may not always be accurate Adapted from Doncaster PH team 26 Information as at 30.6.20
Testing: types of test antigen The antigen test detects the presence of virus in your system at a point in time We need to consider this when we are testing: When was the likely exposure? Are they still in the potential incubation period? Are they likely to be infectious still? An early test may test negative because there is not yet enough virus in system to show up A late test may test positive but this does not necessarily mean someone is still infectious Probably no longer infectious Symptomatic Infected Potentially infectious 27 Information as at 30.6.20
Testing: types of test antibody Antibody test - looks at immune system's response to having had the virus at some time We don t yet know what length or strength of immunity people may develop detecting the presence of antibodies is not the same as detecting immunity Anti-body tests can be used at a population level to give an indication of how many people have had the virus They are not (yet) accurate enough to use at an individual level Timing of the tests are currently affecting accuracy 28 Information as at 30.6.20
Test, Trace, Isolate 29 Information as at 30.6.20
*BUT: we dont know how many pre-symptomatic / asymptomatic cases will test positive Test, Trace, Isolate Index cases identified by screening offering tests to whole populations in high- risk settings regardless of symptoms* Advice given (and followed) Cases potentially prevented Adapted from Doncaster PH team 30 Information as at 30.6.20
*AND: if people test negative, they may be more likely to dismiss any mild symptoms they do develop reinforces the importance of advice regardless of test status Test, Trace, Isolate Asymptomatic or pre- symptomatic cases may not test positive Cases would therefore not be prevented No changes would be made for people testing negative with no symptoms* Adapted from Doncaster PH team 31 Information as at 30.6.20
Testing: what we know and what we dont Antigen testing: recommended on days 1-5 from symptom onset we don t know how long before developing symptoms people might test positive (although research indicates at least some people test positive pre-symptomatically) it takes up to 24-48 hours to get a result back testing speeds are increasing and in some cases available within hours Antibody test: still being improved at present, accuracy is a concern Timing is important Adapted from Doncaster PH team 32 Information as at 30.6.20
Quiz to follow up (1 of 3) List the 3 main symptoms of Covid-19 What are some of the other symptoms? What is the case definition? What makes an outbreak and outbreak? What is the incubation period (definition and duration if you can remember) What is the infectious period? Why is this important? / How is it used? Who is more at risk of Covid-19? What are the main ways it is spread? What are some of the key control measures? 33 Information as at 30.6.20
Quiz to follow up (2 of 3) List 3 examples of good IPC practice Who is vulnerable to infection? How many components of the chain of infection can you remember? What is the most important method of limiting the spread of infection and why? How is an outbreak defined and what are the 3 R s of outbreak management? What is the most important element in effective cleaning? How can you promote Infection Prevention and Control? Adapted from Leeds Community Health Care 34 Information as at 30.6.20
Quiz to follow up (3 of 3) Can you list 3 reasons why testing might be useful? And when might it not be useful? / what are some of the issues to consider before testing? What advice should be given with a negative test result for someone who is a close contact of someone who has tested positive for covid-19? What does the antigen test tell us? What about the anti-body test? 35 Information as at 30.6.20
