Seven other samples from the district are being cross tested at BP Koirala Institute of Health Sciences in Dharan.
"The person is aged 33 and is male. He is currently admitted at Koshi Provincial Hospital in Biratnagar. The test was conducted at National Public Health Lab, Teku, Kathmandu," Dr Bikash Devkota, one of the spokesperson at the Ministry of Health and Population, said on Tuesday.
"Polymerase Chain Reaction (PCR) test of other swab samples are being done. The reports are expected soon," Dr Devkota added.
Till date, 14 cases of COVID-19 have been reported in Udayapur district, which has emerged as the country's hotspot. All of the previous cases in the district are said to be imported.
Four people in Nepal have recovered from COVID-19 so far.
( With inputs from ANI )