Nuwan Thushara had been in great form lately, finishing as the team's highest wicket-taker during the T20 World Cup last month.
Sri Lanka signed off from the T20 World Cup with an 83-run victory over the Netherlands in their inconsequential last group stage match of the T20 World Cup in St Lucia.
Nuwan Thushara has tested positive for Covid-19 ahead of Sri Lanka's departure for the Australia series.