Health authorities are scrambling to identify the missing link to it’s Covid-19 outbreak after another person tested positive.
The latest case is a 21-year-old woman as the state’s cluster, which plunged the Katherine region into lockdown earlier this week, grew to three.
Chief Minister Michael Gunner said the woman had flown from Cairns to Queensland last week and was a household contact of the other two cases.
She tested positive on Friday night and became symptomatic on Saturday.
“Contact tracing has commenced,” Mr Gunner said.
“There may be more exposure sites for Darwin. So it’s critical everyone in the top end pay very careful attention.”
Authorities are trying to get in contact with 20 close contacts of existing cases, having already tracked down another 80.
The new case comes as authorities try to piece together how an unvaccinated man in his 20s, who had not travelled outside the territory, contracted the virus.
The government emphasised that the source of the original infection was unclear and they were undertaking genomic sequencing in a bid to determine the “missing link”.
And while they could not rule out that the 21-year-old woman had brought the virus in from Queensland, they believed that she had caught it from one of the other cases.
“Though it would be nice to think that is the clear connection, the sequencing of infectiousness doesn’t imply that is the source,” acting chief health officer Charles Pain said.
“So unfortunately, we’re still not clear about where this has come from.”
Mr Gunner said there was a “reasonable chance” that the original case had given Covid to the 21-year-old woman, who had only received one dose of a coronavirus vaccine.
“It may be a scenario where someone has come through Darwin, infected one person,” Mr Gunner said.
He added: “I’m feeling positive that we have three cases that are linked and locked. They’re household contacts … What concerns us most at the moment is that we don’t have certainty about how the three people acquired Covid.”