What is the difference between a “confirmed” case and a “probable” case? When is a case considered an "active" case?
“Confirmed” COVID-19 Case
A viral test is the only way to classify a case as a “confirmed” COVID-19 case. If one tests positive, then it is considered a “confirmed COVID-19 case”. This means that the person is currently infected with COVID-19 and are contagious. If one tests negative with a viral test then one is not currently infected with COVID-19.
“Probable” COVID-19 Case
A probable COVID-19 case could mean one of two things: 1) It is likely that you had a COVID-19 infection or 2) It is likely that you have a current COVID-19 infection but it has not been confirmed through a viral test. The only way to confirm if one is currently infected and contagious is through a viral test. There are several ways to classify a “probable COVID-19 case”. In order to be considered a “probable COVID-19 case” it must meet at least two of the following criteria:
• Clinical – Disease investigators use reported symptoms to determine previous or current COVID-19 infection, such as:
- Respiratory distress
- Or chills
• Epidemiological – Disease investigators use lifestyle factors to determine a previous or current COVID-19 infection such as:
- Exposure to a confirmed COVID-19 case,
- Travel to an area where there is a sustained community COVID-19 outbreak
- Or employment in a high risk area (such as hospitals, prisons, or nursing homes)
• Antibody testing – An antibody test determines if you had a COVID-19 infection. If you test positive, this means that you most likely had a COVID-19 infection. Even if one tests positive, this does not mean that you are immune to future COVID-19 reinfections. If one tests negative with an antibody test then it means that you were most likely not infected with COVID-19.
“Active cases” can be either a “confirmed case” or a “probable case”.
Whether a case is considered an active case is determined by context and information availability coupled with a consideration as to the “possibility of being currently infected”. If there is a possibility of being currently infected then it counts as an active case. For example, if a person has symptoms and are connected to a confirmed case, then it would be considered as an active case. If they have no current symptoms but test positive with an antibody test, that would not be an active case because they had it at some point in the past greater than two weeks from date of test.