Google has made a vast dataset of search trends available for researchers in the US to study the link between symptom-related searches and the spread of COVID-19.

The COVID-19 Search Trends symptoms dataset includes aggregated, anonymised search trends for more than 400 symptoms, signs and health conditions, such as cough, fever and difficulty breathing.

The dataset includes trends at the US county-level from the past three years in order to make the insights more helpful to public health, and so researchers can account for changes in searches due to seasonality, the company said in a statement on Wednesday.

Using the dataset, researchers can develop models and create visualisations based on the popularity of symptom-related searches.

"This sample visualisation is based on search volume for fever across the U.S. This visualisation does not reflect the dataset's user interface but shows what can be generated," Google said.

Researchers could use this dataset to study if search trends can provide an earlier and more accurate indication of the reemergence of the virus in different parts of the country.

The dataset is available in Google Cloud's COVID-19 Free Public Dataset Programme and is downloadable from Google Research at Open COVID-19 Data GitHub repository.

"No personal information or individual search queries are included," Google said.

This early release is limited to the US at the moment and covers searches made in English and Spanish.