The observation pathway can change
A new testing service may identify cases that were previously missed. A reduction in testing can lower reported counts without a matching reduction in infections. Changes in awareness or reporting requirements can also affect the series.
This does not make every trend artificial; it makes the detection process part of the interpretation.
A simple pathway check
- Who is likely to seek care or testing?
- Who is eligible and able to obtain a test?
- Which results enter the reporting system?
- How quickly and completely are they reported?
Different groups may experience different barriers at each step.
Do not invent one universal multiplier
Estimating total infections from reported cases requires evidence and assumptions that can change over time. A multiplier from one setting or period may not transfer.
Triangulate with other observations
Hospitalizations, mortality, wastewater, surveys, or other sources can add information, but each has its own selection and delay. Agreement across appropriately interpreted sources can strengthen a conclusion; disagreement can reveal a useful question.
Describe reported cases as reported cases unless a valid estimation method supports a broader claim. Precision in that label helps readers understand both the value of surveillance and the part of the population it cannot directly observe.
