It was February and the world was just waking up to the realities of Covid-19 as the highly contagious disease ravaged nations and locked down economies.
"I had been following the news trends at the time so when he walked into my consulting room with his complaints, he had a fever, it was high grade, headache, muscle pain and fatigue. I took his medical history and he said he had just come from Italy ... so I knew it was likely Covid-19," she told CNN in an Instagram live interview
The unnamed Italian man had arrived in the country from Milan just 48 hours before he visited the private medical center where Allison worked.
Trying not to panic about the risk of contracting the disease herself, Allison said she counseled the man and gave him a face mask.
"I told him I would need to isolate him and he was very cooperative," she said.
'A scary experience'
She didn't know it at the time but Allison, 32, had just detected Nigeria's first confirmed case of coronavirus and her quick thinking has attracted praise from many Nigerians who hailed her a hero for helping to contain the spread of the virus in Africa's most populous nation.
The Ogun state government recently celebrated Allison and hailed her "singular brilliance."
"The Ogun State Government appreciates the young female doctor who suspected the index case in Nigeria in our State, Dr. Amarachukwu Karen Allison of Lafarge Nigeria. Her singular brilliance led to the early diagnosis and rapid containment of the first Covid-19 infection," the statement read.
The man was later transferred to an isolation center in the neighboring city of Lagos and Allison was promptly placed in quarantine.
"It was a really scary experience and I am so thankful that I tested negative," recalled Allison, who said it was her third experience of being quarantined.