The Truth Behind the Zika Numbers

Often times when the figures of confirmed laboratory cases of diseases such as Chikungunya and Zika are reported by officials to the media, we normally get surprising reaction from the public. Comments like; “those figures can’t be true because my whole village had Zika” are not uncommon. 

The reported figures are often laboratory confirmed positive cases. These cases do not represent everyone who have been infected. The figures are only what is described as the “tip of the iceberg” as demonstrated in the diagram of the iceberg phenomenon bellow.


In the context of the Zika outbreak the reported cases are the persons who have been infected with Zika and were symptomatic and then sought medical attention. They were the ones who were eligible for testing and then got tested. As is seen in the iceberg phenomenon only a small percentage of all the infected persons end up being laboratory confirmed positive cases.

The iceberg phenomenon is important and provides valuable information for public health decision making. It gives an indication of the magnitude of the infection so that action can be taken to reach those who cannot be seen and are ‘under the water’.

Dr. James Hospedales, Executive Director – Caribbean Public Health Agency (CARPHA)

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