A vaccination campaign in the immediate area is to begin over the next week.
Ukraine is currently racing to vaccinate children against polio after a rare case was reported in a toddler earlier this month.
The case, present in a 17-month-old girl, marks the first in Europe in five years.
The child was found to have the virus when she showed acute flaccid paralysis, a weakness of the limbs and a symptom of polio. Her long-term prognosis is yet to be determined.
Her illness was caused by poliovirus type 2 (cVDPV2), which, unlike wild polio, is the result of incomplete vaccination campaigns.
Six of her siblings were also found to have the virus, though they were asymptomatic.
The country alerted the World Health Organisation (WHO) to the case on October 3, announcing it to the rest of the world three days later.
According to WHO, just one case of polio is enough to be considered an outbreak.
As a result, a regional biological emergency was declared in the Rivne area in the northwest of the country.
In order to prevent further spread, health officials are now racing to vaccinate all young children – regardless of existing polio vaccination status – in the immediate area against the virus in the coming days.
A vaccination campaign targeting under fives in the wider region will also be rolled out in the next 90 days.
Technical officer for vaccine-preventable diseases and immunisations at WHO Europe, Dr Shahin Huseynov, told the Telegraph that the key to a high-quality outbreak response is a successful vaccination campaign.
“If a population is fully immunised against polio, it will be protected against both wild polio and VDPVs [vaccine-derived polioviruses],” he said.