Burundi has declared a national public health emergency after polio was detected in a 4-year-old and two other children who had been in contact with the child.
The polio outbreak is Burundi's first in more than 30 years.
The landlocked African country is preparing a vaccination campaign targeting eligible children, from newborns to 7-year-olds. It will be ready in a few weeks.
In addition to the children, health officials found five polio samples in its surveillance of wastewater, confirming the presence of circulating poliovirus type 2. Early detection is critical in containing an outbreak of the disease.
Type 2 infections can occur when the weakened strain of the virus contained in the oral polio vaccine circulates among under-immunized populations for long periods.
The highly infectious disease is also spread through contaminated water and food or contact with an infected person.