"Laboratory tests conducted at Kabaile Mobile Laboratory in Kagera and later confirmed in Dar es Salaam, identified one patient as being infected by Marburg virus," she said at a press conference that was also attended by World Health Organisation director general Tedros Adhanom Ghebreyesus in Dodoma, a town in the centre of the country.
Last week Tanzania's health minister denied there was an outbreak in the African country, saying no one had tested positive for the viral infection.
The denial came after the WHO said it had received reliable reports that eight people had died of suspected cases of the virus in the same area on January 10.
Victims had presented with typical Marburg symptoms including headache, high fever, back pain, diarrhoea, vomiting blood, muscle weakness and external bleeding.
The viral hemorrhagic fever has a fatality rate as high as 88 per cent, and is from the same virus family as the one responsible for Ebola, which is transmitted to people from fruit bats endemic to parts of east Africa.
Hassan said the government had strengthened its response efforts and that a rapid response team had been dispatched to the area to follow up on all suspected cases and try to contain the outbreak.
At least 25 suspected cases had all tested negative, she said.
Tedros said the WHO would release $US3 million ($A4.8 million) from the WHO's contingency fund for emergencies to support efforts to contain the outbreak in Tanzania.
This is the second reported outbreak of the disease in Kagera.
In 2023, a total of nine cases were reported and six deaths.
"The government's investments in response to the last outbreak has built capacities that, I hope, will enable Tanzania to bring this latest outbreak under control as soon as possible," Tedros said.
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