“As of now, we have 53 primary contacts,” said Nigeria Centre for Disease Control and Prevention (NCDC) boss Jide Idris.
The count was up from 44 people who had come in contact with a woman who fell ill with Ebola in the Nigerian capital Abuja.
The woman, the 42-year-old wife of a Swiss embassy staff worker based in Abuja, had been travelling in Uganda with her husband before returning to Nigeria. She is receiving treatment and remains the only confirmed case.
A test on a suspected case, in Rivers State, in the Niger Delta, came back negative, Idris told reporters.
The initial 44 contacts were health care workers, while the additional nine comprise more health staff as well as members of the infected woman’s family and household staff, Idris said.
The World Health Organization has warned that Africa is facing a “complex” Ebola outbreak with the virus now present in west, east and central Africa.
Health authorities in Nigeria successfully stemmed a previous Ebola outbreak a decade ago but some experts are worried about how much the illness could have spread in the time between the woman’s arrival – October 3 – and her diagnosis, announced on Tuesday.
Nigerian authorities have announced enhanced screenings for international airport arrivals.
Nigeria last week announced west Africa’s first case from an outbreak ravaging Democratic Republic of the Congo – an imported case of the Bundibugyo strain, for which there is no vaccine or specific treatment.
The DRC has recorded more than 4,600 deaths since it declared its 17th Ebola outbreak in May.
Uganda has had 20 cases, including two deaths, on its territory but the World Health Organization officially declared it Ebola-free. Almost all the cases were people who had visited DRC.
Uganda said on Sunday its nationals returning from DRC would have to spend 21 days in quarantine.
Ebola is transmitted through contact with bodily fluids and causes severe haemorrhagic fever.
Kenya has reported two deaths this month.
The country had not reported a single case until a Kenyan man who had been living in DRC died after returning home. The second death was a close contact of the man, authorities said. As of Friday the country had seven Ebola cases in isolation. (AFP)