public health surveillance is the ongoing systematic collection analysis and reporting of health-related data to inform planning implementation and evaluation of public health actions and policies now that might sound like a long and complicated definition but as we walk through how it is that surveillance is done and how it is that it's used that definition will begin to make a lot of sense now while most of the examples in this video are going to be about infectious disease surveillance i want you to note that the principles that we're going to talk about can be applied to non-communicable disease injuries health services uptake environmental hazards and other health issues this is the mechanism whereby we keep our finger on the pulse of what's going on in the community so let's talk about what surveillance is used for firstly it's used to inform individual case management and to provide timely treatment and prevent spread when a disease is identified next it's used to recognize monitor and control outbreaks it's also used to detect and characterize new diseases it can be used to measure changes in incidence and to track changes in risk factors it can be used to evaluate control measures to enable research and to inform policy now let's talk about how public health surveillance is undertaken the first step is to identify clear objectives of the surveillance programs and to describe what we call the case definition now the case definition usually includes clinical epidemiological and lab criteria that can distinguish between possible probable and confirmed cases of that disease you need a case definition to provide clarity as to whom should be included as a case so that different people reporting cases from different parts of the country and at different points in time are all talking about the same disease all of this data is comparable and can be aggregated and the same analysis and reporting can be done over time next we need to collect the actual data now this can come from clinicians from labs from ports and other sources for some diseases there is a statutory requirement that cases are notified to public health officials and we'll talk more about the different mechanisms that we use to collect data and how that relates to the different types of surveillance in just a minute then of course the data needs to be stored and because this data relates to individuals personal medical records it has to be collected and stored securely and finally the data has to be analyzed and reported on to relevant stakeholders to ensure that public health actions can be taken and to inform health policy now let's talk about different types of surveillance a super quick interruption to this video to say thanks to nested knowledge nested knowledge sponsored this channel and i absolutely love them nasa knowledge is an online platform that you can use to do literature review and systematic lit review and what i love about this platform is that i'm using it for the entire process beginning to end all the way from search screening tagging extraction all the way through to actually writing the manuscript creating a living document online i've got my entire team using it so we collaborate different people doing different parts of the process i used to hate litterview now i love it if you want to love lit review check out nested knowledge click on the link in the description below and without further ado on with the video firstly there's passive surveillance this is the ongoing collection of data from what are usually notifiable diseases the systems are in place and so the cost of running passive surveillance is low so because this is done over time changes in trends can be detected so for example a change in the infectivity of a virus or a change due to a public health intervention can be detected now one of the limitations of passive surveillance is that there's typically under-reporting so of all of the cases of a disease only some become symptomatic and of those only some present to a healthcare provider and of those only some have a diagnostic test performed that confirms the diagnosis and as you can imagine by contrast there's also active surveillance here public health proactively contact clinicians labs and affected people in the public to collect information about the disease and about the affected people including information about exposures and demographic and social descriptors this is often done during an outbreak or for cases of high consequence disease or for cases from vulnerable communities it can also take the form of a health survey on a community or even a health survey of an entire country now this data is more complete and is of a better quality than you would get from passive surveillance but it's more expensive to collect let's look at some other types of surveillance firstly there's zero surveillance this involves testing blood samples in a sample of the population for various markers like antibodies against infectious agents due to past infections or vaccinations if interpreted correctly this type of surveillance can be used to make inference about the population level of immunity to a disease it can also be used to identify age cohorts at risk and can be used to plan a vaccination program sentinel surveillance here selected healthcare providers and it could be hospitals or general practitioners provide health data on cases presenting with specific diseases or conditions and data from the sample can be used to make inference about the population level incidence and the characteristics of people being affected sentinel surveillance can be used to monitor disease trends and can be used to detect outbreaks next whole genome sequencing surveillance whole genome sequencing characterizes the genetic makeup of a sample of disease causing agents to identify genetic changes that might indicate a change to infectivity for example or severity of disease or provide information about the chain of transmission caused by that agent for example whole genome sequencing might be done on a sample of covert 19 cases so that a new variant of concern could be detected if just one percent of the cases are identified with that variant and then there's syndromic surveillance these could be respiratory symptoms and non-specific fevers or even absenteeism from work or school this is an excellent early warning system to identify illness in a community now the next video that i suggest you watch is one that i made a while ago on how to interpret an epidemiological curve i hope you found this useful remember to subscribe to this channel if you haven't already leave a comment below and i'll try and respond please do share this video with others that you think might find it useful have a great day don't do drugs which do your best to speak to you soon take care bye