Freetown (AFP) - Sierra Leone on Wednesday berated the "selfish and shameful" behaviour of people risking a resurgence of the Ebola virus by flouting quarantine restrictions, as authorities announced a spike in cases.

The country's National Ebola Response Centre (NERC) spoke out as the World Health Organization (WHO) revealed the west African nation and its neighbour Guinea had seen cases quadruple in a week.

Palo Conteh, head of the government-run NERC, told reporters in the capital Freetown a man who went on the run despite being under quarantine was responsible for the enforced isolation of 52 people.

"Some of the 52 may be infected because of a selfish and shameful act of a small number of people," he said.

Saidu Conteh escaped a sealed-off section of Freetown's densely-populated Moa Wharf slum after his girlfriend died of Ebola, said the NERC chief, who is no relation.

He evaded capture for a week but died in a treatment unit on Sunday, two days after being tracked down at another residence in Freetown by expert Ebola contact tracers.

Palo Conteh said health officials had removed 52 people from their building and were monitoring them at an isolation unit on the outskirts of the capital.

The group includes the escapee's mother and a nurse who was said to have been massaging him and washing his clothes, despite repeated government warnings that Ebola spreads through physical contact.

- Family on the run -

"You will not survive by running away from quarantine or by caring for the sick in hiding," the NERC chief said.

A friend who escaped with Saidu Conteh was eventually rounded up around 160 kilometres (100 miles) to the southeast of Freetown, he added.

The problem is not just restricted to the capital according to the NERC, which said another five people had escaped their quarantined home in the northern district of Kambia, near the border with Guinea.

"They are all family members and we are on the look out for them as we have to ascertain their status," NERC coordinator Zylatu Cooper told a private Freetown radio station.

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The government says 578 patients are in quarantine across the country, most in the Western Area which includes the capital.

The seven days ending Sunday "saw the highest weekly total of confirmed cases of Ebola virus disease for over a month", the WHO said in its latest update.

A full 35 new cases were reported during the week in Guinea and Sierra Leone, up from just nine a week earlier.

According to the latest figures, the outbreak has infected 26,933 people and killed 11,120, mainly in Guinea, Sierra Leone and neighbouring Liberia, which was declared Ebola-free on May 9.

Guinea, where the outbreak began in late 2013, was hardest hit last week, with 27 new cases reported, compared to just seven the week before.

Eleven of those cases were reported in the western prefecture of Dubreka, and most of them appeared to be linked to people who attended the funeral of someone believed to have died from Ebola in mid-April.

- Health worker infected -

Eleven other cases were reported in the prefecture of Forecariah, but it was the five remaining cases found in the northwestern prefecture of Boke, which borders Guinea-Bissau, that had experts most concerned.

WHO said experts had been sent to the border to determine if possible cases may have crossed over, and ensure that anyone known to have been in contact with Ebola patients is being tracked.

Sierra Leone, which had appeared to be heading in the same direction as neighbouring Liberia, meanwhile saw the number of new cases shoot up to eight from just two a week earlier.

The increase in Sierra Leone brought to an end "a sequence of three consecutive falls in weekly case incidence," the WHO said.

The UN agency also deplored that, for the first time in five week, a Sierra Leonean health worker had tested positive for Ebola.

The health worker had been working at an Ebola treatment centre near Freetown -- the same facility where an Italian male nurse who tested positive for Ebola after returning home had worked.

Ebola, one of the deadliest viruses known to man, is spread only through direct contact with the bodily fluids of an infected person showing symptoms such as fever or vomiting.

People caring for the sick or handling the bodies of people infected with Ebola are thus especially exposed.

Since the beginning of the outbreak, 869 health workers have been confirmed to be carrying Ebola, and 507 of them have died, according to the WHO.