A doctor who treated an Ebola-stricken Liberian has fallen ill with the disease, the first confirmed domestic case in the megacity of Lagos, Nigeria, authorities said Monday.

Nigerian Health Minister Onyebuchi Chukwu said the doctor had been treating Liberian Patrick Sawyer, 40, who flew to Lagos from Liberia on July 20 and fell ill while on the plane. He collapsed at the airport, was taken to a hospital and died in quarantine five days later.

An additional eight Nigerians are hospitalized under quarantine with suspected Ebola, and 61 more are under observation.

Six of those now in quarantine were initially placed under observation in the community, but were hospitalized over the weekend after exhibiting symptoms that may be those of Ebola.

"The new case is one of the doctors who attended the Liberian Ebola patient," said Chukwu, according to Nigeria's Vanguard newspaper.

There are fears Ebola could spread quickly throughout Nigeria if it takes hold in Lagos, one of the continent's most crowded cities.

Ebola was first reported in the West African nation of Guinea in February, and swiftly spread to neighboring Sierra Leone and Liberia.

More than 1,300 people have been infected and about 730 have died, according to World Health Organization figures released last week.

Of the fatal cases, at least 60 are doctors, nurses and health workers.

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