The research includes people who died from Covid-19 and non-Covid-19 illnesses
It's to find out the scale of the virus in nursing homes.
Yesterday saw the death toll rise to 530, after a further 44 patients died after being infected with Covid-19.
There have been 335 outbreaks in residential care settings, including 196 in nursing homes.
Kathleen McLellan, from the Department of Health, says the census will inform how the state tries to stop the spread of Covid among older people:
