We’ll take a look at what an outbreak is? How it’s detected, investigated and controlled.

First of all, what is an outbreak? 

Basically, an outbreak is when there’re more cases appear what’s normally expected in the population in the given area and at thegiven time. The terms epidemic and outbreaks are sometimes use interchangeably.

How do we detect outbreaks?

 Well, there’re several different ways. The existence of outbreak maybe known through a variety of surveillance methods. These include passive surveillance, which is monitoring collected health data, active surveillance when health information is actively sorted out. Sentinel surveillance where selected groups of institutions provide health data. Syndromic surveillance which is the monitoring of illness syndromes, or though a variety of other sources of information including thesocial media, news.

Once a decision is taken to investigate the outbreak, it go though a few systematic steps. The number of steps, order and content can vary, and several steps can be done at the same time. An outbreak investigation  consist of confirming whether there is anoutbreak, describing it, determining the cause of the outbreak, and then implementing control methods so that it doesn’t spread further or happen again.

Let’s take a look at the steps in a bit more detail. 

Confirming there is an outbreak is the first step of the investigation.

To determine whether there’re more cases exceed what’s expected , we need to know the baseline level of  illness net population for that given time. Then we can compare with the level of illness we are seeing to see whether there is an increase. However, it’s important to know that even if there’re more cases than expected, other cause of disparate increase, such as a sudden increase of testing, a lab or diagnosis error, or a sudden increase in population, needs to be ruled out. To work out what’s causing the outbreak and help to decide what’s 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 action that can be taken to control the outbreak, especially the source and motive 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 inside into who’s infected, where the illness occurs and other characteristic of the outbreak. Let’s take a close look. To describe the outbreak, investigators need to figure out who should be considered as 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 a case. Generally there is a criteria for a 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 systematical way and information about the cases is recorded. This is usually done by questionnaires, and summarized by time, person and place. Let’s have a look at each one of them, because each of these provide useful inside into the outbreak.

By describing the occurrence of the cases over time, investigators can look at how the diseases had developed over time. This is typically displayed in the graph that shows the number of cases in the y-axis, and time on the x-axis. This type of graph is known as an epidemic curve. There are two common patterns of epidemic curves. The first is the point source outbreak, this happens when the outbreak is from a point-source. For example, if there is an outbreak of gastroenteritisafter eating a contaminated dish served in the restaurant, the typical pattern of this is a sharp rise in cases followed by a rapid decline. The other one is propagated outbreak.  This pattern is commonly an outbreak with the infection is passed from person to person and the first wave of the infection is the 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 geographical spread ofillness, and identify there’re any clusters. Modern mapping tools and Geographic Information Systems technology has become important tools of mapping and tracking outbreaks.

Describing people who are affected by the outbreak, for example by age, sex, occupationand ethnicity, can provide useful insides into the disease.  It allows the investigator to figure out whois at further risk.

The second step about the outbreak investigation which is how to describe an outbreak.

Figuring out what causes the outbreak is the next part of the outbreak investigation. From the information that is available from the steps before, investigator might have an explanation for the likely cause of the outbreak. This is also known as the hypothesis. Now if the pathogen that is the cause of the outbreak is already known, then it can provide useful information to guide investigators to the likely source and motive transmission. For example, in an outbreak caused by V. Cholera, investigator will look at contaminated water as the potential source of the outbreak. If it is Salmonella outbreak, it’s likely due to the 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 the analytical epidemiological studies. The two most commonly used types of analytical study in outbreak investigation are cohort studies and case-control studies.

These studies can determine how likely it is that a certain factor is the cause ofthe outbreak. In addition to analytical epidemiological studies, an environmental investigation can also help to confirm the hypothesis. For example, in a foodborne outbreak, the environmental investigation couldidentify factors like contaminated eggs, inappropriate food storage or poorhygiene standards that may have contributed to or cause the outbreak.Laboratories are very useful as they can provide microbiological information to confirm the hypothesis.

That concludes our third step of determining what could cause the outbreak.

Now let’s discuss the primary goal of investigating an outbreak- control. Controls canhappen at any stage of the outbreak investigation, and can be targeted at any step of the transmission pathways between agent, host and environment.

Control measures include behavioural interventions, like using the mosquito repellent toprevent against mosquito-borne disease, vaccination like given measles vaccine during a measles outbreak, medication like ivermectin for scabies outbreaks, environmental measures like insecticide spraying during malaria outbreak, or improving water quality during cholera outbreak. Infection control measures like isolating infectious cases wearing appropriate personal protective equipment and disinfection of medical equipment to restrict further of the infection.Providing targeted and appropriate health education, we ensure that those who are sick, we will know what to do to stop the disease, and those who are not sick, we will know what to do top revent getting sick. After control measures are implemented,  there should be active surveillance to monitor outbreak to  make sure that the measuresare working.

That was aquick look at different ways that outbreak can be controlled.

Now let’s talk about communication. This is an important aspect of manage in anyoutbreak, 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 organization or external to organization, like other organization or the public. Communication to the public is important,especially to those who are affected by the outbreak. It allows them to adopt protective behaviours, helps with diseases surveillance and reduces anxiety,confusion and misinformation. The media can be a useful partner at outbreak communication. Sharing information about outbreak using online forms or scientific journals, and describing what measures will be taken to be effectiveand what lessons will be learnt to help us to manage future outbreak.

Finally,once the investigators are satisfied that the outbreak is undercontrol, it must be declared over.

 For infectious diseases, this is usually when there is no case after 2 incubation periods passed.

And that’s a quick look at infectious diseases outbreak. We have looked at what they are,how do they detected, steps involve an outbreak investigation, including ways which outbreaks are controlled.