[Music] welcome to this video on outbreak investigation we'll take a look at what an outbreak is how its detected investigated and controlled first of all what is an outbreak basically an outbreak is when there are more cases of illness than what's normally expected in a population in a given area and at a given time the terms epidemic and outbreak are sometimes used interchangeably how do we detect outbreaks well there are several different ways the existence of an outbreak may be known through a variety of surveillance methods these include passive surveillance which is monitoring routinely collected health data active surveillance when health information is actively sought out Sentinel surveillance where selected groups or institutions provide health data syndromic surveillance which is the monitoring of illness syndromes or through a variety of other sources of information including the social media news or even hearsay once a decision is taken to investigate the outbreak it goes through a few systematic steps the number of steps order and content can vary and several steps can be done at the same time but in essence an outbreak investigation consists of confirming whether there is an outbreak describing it determining the cause of the outbreak and then implementing control measures so that it doesn't spread further or happen again let's take a look at the steps in a bit more detail confirming that there is an outbreak is the first step of an outbreak investigation to determine whether there are more cases of illness than what's expected we need to know the baseline level of illness in that population for that given time then we can compare it with the level of illness we're seeing to see whether there is an increase however it's important to note that even if there are more cases than expected other causes of this apparent increase such as a sudden increase of testing a lab or diagnostic error or a sudden increase in population needs to be ruled out to work out what's causing the outbreak and to help decide on the best control method it's necessary to verify the diagnosis this is usually done by reviewing the clinical and laboratory findings now at this stage there could already be immediate actions that can be taken to control the outbreak especially if the source and mode of transmission is known to proceed with the outbreak investigation it may be necessary to get a team together the size of the team will depend on the nature of the outbreak once the outbreak has been confirmed the next step is to describe the outbreak describing the outbreak provides an insight into who's affected where the illness occurs and other characteristics of the outbreak let's take a closer look to describe the outbreak investigators need to figure out who should be considered a case determine whether all the cases have been found and then describe the cases to figure out who should be considered as a case there needs to be a case definition this sets out the criteria which need to be met in order to classify a person as the case generally there are criteria for time place person clinical and laboratory features that must be satisfied before a person can be classified as a case once there is a case definition cases are looked for in a systematic way and information about the cases is recorded this is usually done by using questionnaires and summarized by time person and place let's have a look at each one of them because each of these provide useful insight into the outbreak by describing the occurrence of cases over time investigators can look at how the disease has developed over time this is typically displayed in a graph that shows the number of cases in the y-axis and the time on the x-axis this type of graph is known as an epidemic curve there are two common patterns of an epidemic curve the first is a point-source outbreak this happens when the outbreak is from a point source for example if there's an outbreak of gastroenteritis after eating a contaminated dish served at a restaurant the typical pattern of this is a sharp rise in cases followed by a rapid decline the other one is a propagated outbreak this pattern is common in outbreaks where the infection is passed from person to person and the first wave of infections is a source for the next wave the typical pattern of this curve is a series of progressive peaks of illness the other descriptor is place this can provide information on the geographical spread of illness and identify if there are any clusters modern mapping tools and geographic information systems technology have become important tools in mapping and tracking outbreaks describing people who are affected by the outbreak for example by age sex occupation and ethnicity can provide useful insights into the disease it allows investigators to figure out who is at further risk and that's a look at the second step of outbreak investigation which is how to describe an outbreak figuring out what caused the outbreak is the next part of the outbreak investigation from the information that is available from the steps before investigators might have an explanation for the likely cause of a outbreak this is also known as a hypothesis now if the pathogen that's the cause of the outbreak is already known then it can provide useful information to guide investigators to the likely source and mode of transmission for example in an outbreak caused by cholera investigators would look at contaminated water as the potential source of the outbreak if it's a salmonella outbreak it's likely due to contaminated eggs or meat products if however it's not very clear investigators need to test and confirm the hypothesis that was developed this is usually done with an analytical epidemiological study the two most commonly used types of analytical studies and outbreak investigations are cohort studies and case control studies these studies can determine how likely it is that a certain factor is the cause of an outbreak in addition to the analytical epidemiological studies an environmental investigation can also help confirm the hypothesis for example in a foodborne outbreak the mental investigation could identify factors like contaminated eggs improper food storage or poor hygiene standards that may have contributed to or caused the outbreak laboratories are very useful as they can provide microbiological information to confirm the hypothesis and that concludes our third step of determining what could have caused the outbreak now let's discuss the primary goal of investigating an outbreak control control can happen at any stage of the outbreak investigation and can be targeted at any step of the transmission pathways between the agent host and the environment control measures include behavioral interventions like using mosquito repellents to prevent against mosquito-borne diseases vaccinations like giving measles vaccine during a measles outbreak medication like ivermectin for scabies outbreaks environmental measures like insecticide spraying during a malaria outbreak or improving water quality during a cholera outbreak infection control measures like isolating infectious cases wearing appropriate personal protective equipment and disinfection of medical equipment to restrict further spread of the infection providing targeted and appropriate health education will ensure that those who are sick will know what to do to stop spreading the disease and those who are not sick will know what to do to prevent getting sick after control measures are implemented there should be active surveillance to monitor the outbreak to make sure that the control measures are working that was a quick look at the different ways that an outbreak can be controlled now let's talk about communication this is an important aspect of managing any outbreak large or small communication is about making sure that accurate timely information gets to the right people at the right time this can be those who are internal to the organization or those who are external to the organization like other organizations and the public communicating to the public is important especially to those who are affected by the outbreak it allows them to adopt protective behaviors helps with disease surveillance and reduces anxiety confusion and misinformation the media can be a useful partner and out great communication sharing information about the outbreak using online forums or scientific journals and describing what measures were taken that were effective and what lessons were learned can help others manage future outbreaks finally once the investigators are satisfied that the outbreak is under control it must be declared over for infectious diseases this is usually when there are no cases after two incubation periods have passed and that's a quick look at infectious disease outbreaks we had a look at what they are how they're detected and steps involved in an outbreak investigation including ways in which outbreaks are control