Nigeria's centre for disease control has confirmed the outbreak of Yellow Fever in Bauchi State.
The Director General of the NCDC, Chikwe Ihekweazu, in a statement on Friday said the agency was first notified of the outbreak on August 29.
He said the agency received the report of a confirmed case of yellow fever in Kano State from a laboratory in its network.
Also, the Bauchi State government confirmed an outbreak of the disease in the state on Thursday.
The Punch Newspaper reported that the Executive Secretary, Bauchi State Primary Healthcare Development Agency, Rilwan Mohammed, said the Ministry of Health had a yellow fever case linked to Yankari Game Reserve.
The outbreak is also linked to the death of four students of the College of Education, Waka-Biu, Borno.
The students had gone on a field trip to Yankari Game Reserve, in Bauchi State as part of their course work.
On Wednesday, PREMIUM TIMES reported that at least four of the people had been confirmed dead and 12 hospitalised.
According to the statement, three of the confirmed cases are residents of Alkaleri Local Government Area (LGA).
The fourth case is a tourist who was visiting Kano State and also visited the Yankari Games Reserve in the same LGA in Bauchi.
This development is coming weeks after confirmed cases of yellow fever outbreak in Ebonyi State.
The outbreak in Ebonyi State began on July 15 with some deaths recorded.
Mr Ihekweazu said subsequent investigations led by the Kano State Epidemiology Team established that the confirmed case of yellow fever "was from a patient who visited the Yankari Game Reserve in Bauchi, in August with his father.
The father died with similar symptoms before a sample could be collected and tested, he said.
Also, the Borno State Epidemiology Team on Tuesday had reported deaths among students of Waka College of Education in Biu LGA Borno State.
"Of the 95 Students that visited the resort (Yankari Game Reserve), eight of them developed symptoms and six had died as at the time of the report. The others are in a stable condition. Samples from these cases are being tested," the NCDC said.
NCDC added that three more cases were confirmed in Bauchi "due to intensive surveillance".
The three new cases are all residents of Alkaleri Local Government Area of Bauchi.
"Altogether, we can confirm four cases of yellow fever in people that either live in or have visited Bauchi in the last one month," he said.
Since it was notified, the NCDC said it has been collaborating with the state epidemiologists and the World Health Organisation country office to investigate these events.
"We have deployed a rapid response team to support Bauchi State to carry out further in-depth investigations, including case finding, risk communications, and support the management of cases.
"Samples of the other suspected cases from Bauchi and Borno states are currently being transported to the NCDC National Reference Laboratory in Abuja for further testing," it said.
NCDC said it has also activated the Emergency Operations Centre to coordinate the response to the outbreak.
Mr Ihekweazu said the yellow fever vaccine is available for free in all primary healthcare centres in Nigeria as part of the routine childhood immunisation schedule.
"We encourage every family to ensure that children receive all their childhood vaccines.
"In addition to the vaccine, the public is advised to keep their environments clean and free of stagnant water to discourage the breeding of mosquitoes and ensure the consistent use of insecticide treated mosquito nets, screens on windows and doors to prevent access for mosquitoes.
"Hikers, park visitors and people engaged with activities in the wild are also encouraged to be vaccinated against yellow fever."
Yellow Fever virus is spread through bites of infected mosquitoes.
There is no human-to-human transmission of the virus. Yellow fever is a completely vaccine preventable disease and a single shot of the yellow fever vaccine protects for a lifetime.
The symptoms of yellow fever include yellowness of the eyes, sudden fever, headache and body pain.