A doctor who worked in West Africa with Ebola patients was in an isolation unit in New York City yesterday after testing positive for the virus, becoming the fourth person diagnosed with the disease in the United States and the first in its largest city.

Craig Spencer, 33, was quarantined at Bellevue Hospital on Thursday, six days after returning from Guinea, unnerving financial markets amid concern the virus may spread in the city. The three previous cases were in Dallas.

Three people who had close contact with Spencer, a physician who volunteered for the humanitarian group Doctors Without Borders, were quarantined for observation. The doctor’s fiancée was among them and was quarantined at the same hospital, and all three were still healthy, officials said.

Doctor was quarantined six days after returning from Guinea

Meanwhile, Nina Pham, one of two nurses infected with Ebola after treating the first patient diagnosed with the disease in the United States, was declared virus-free.

US stock markets shook off Ebola fears yesterday, with the S&P 500 rising 0.5 per cent to 1,959.71 by early afternoon. Stock futures had sold off late Thursday evening after the New York City case was confirmed. US Treasury bonds, which earlier rallied on safe-haven bets, were little changed.

“I think the fears are a bit overdone, said Caroline Vincent, European equities fund manager at Cavendish Asset Management. “In previous cases, such as avian flu, the virus ended up being contained quite quickly.”

The worst Ebola outbreak on record has killed at least 4,877 people and perhaps as many as 15,000, mostly in Liberia, Sierra Leone and Guinea, according to the World Health Organisation (WHO).

The WHO set out plans yesterday for speeding up development and deployment of experimental vaccines, saying hundreds of thousands of doses should be ready for use in West Africa by the middle of next year. The Republican-led House Oversight and Government Reform Committee was holding a hearing yesterday to examine the Obama administration’s Ebola response, featuring testimony from government officials, a nurse’s union representative and a humanitarian group working to control the outbreak in Africa.

New York City Mayor Bill de Blasio and state Governor Andrew Cuomo sought to reassure New Yorkers they were safe, even though Spencer had ridden subways, taken a cab and visited a bowling alley between his return from Guinea and the onset of symptoms.

“There is no reason for New Yorkers to be alarmed,” de Blasio said at a news conference at Bellevue Hospital. “Being on the same subway car or living near someone with Ebola does not in itself put someone at risk.”

Cuomo said that, unlike what happened in Dallas, New York officials had time to thoroughly prepare and drill for the possibility of a case emerging in the city.

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