Lassa fever, which has been likened to the Black Death, has now killed two doctors and a nurse in the country, wth one other patient still languishing in hospital.
Some medics fled the hospital in fear after the deaths, according to local media.
A rapid response team has now been dispatched by the World Health Organisation and Nigeria Centre for Disease Control (NCDC) to deal with the latest outbreak in Ebonyi State.
The virus is spread when people come into contact with food and household items contaminated with rat urine or faeces.
It can then be passed between humans through blood or other bodily fluids.
Symptoms include a fever, facial swelling, muscle fatigue and bleeding from the mouth or nose.
Death can follow within two weeks of the virus taking effect.
Chief Executive Officer of the NCDC, Dr Chikwe Ihekweazu, said: “The NCDC has provided urgently required medical supplies and drugs to support case management in the state.
“Health care workers in health facilities are particularly at risk of contracting the disease, especially where infection prevention and control procedures are not strictly adhered to.
“We therefore strongly advise that health care workers practice universal care precautions while handling patients at all times, not just when Lassa fever is suspected.”
There is no vaccine for the illness but people are being advised to keep their homes clean and store food away to stop encouraging rats.
Dr Uche Unigwe said there were now 20 cases of the virus across the country.
The health official said medical workers would be targeting all health facilities in the state alongside rural villages in a desperate bid to stem the outbreak.
Dr Unigwe said: “When the disease strikes, it does not choose destination or whom to attack.
“The most important thing is to develop a high index of suspicion so that medical workers can easily identify Lassa fever when they look at patients and protect themselves.”
The latest fatalities follow the death of a young girl in Uganda from a brutal “eye-bleeding fever”.
Her tragic death has sparked massive fears about a health crisis after another three people were said to have died in the country.