The risk to public health has been raised to very high in the Democratic Republic of Congo by the World Health Organization, after a case of Ebola was confirmed in a major city.
The first definite case of the deadly virus in the cityMbandaka, which has a population of around 1.5million, was described as a major, major game-changer in the outbreak, by WHO deputy director-general of emergency preparedness and response, Dr Peter Salama.
The fear now is that the disease, which has been linked to the deaths of as many as 25 people so far this year, could spread much faster in a city than in remote, rural areas, where most cases had been reported to date.
The WHO also raised the risk level to high from moderate in the region, adding: The confirmed case in Mbandaka, a large urban centre located on major national and international river, road and domestic air routes increases the risk of spread within the Democratic Republic of the Congo and to neighbouring countries.
The first Ebola case of this outbreak was announced last week in the city of Bikoro, 93 miles from Mbandaka, where there were a further three suspected cases.
A WHO statement said there had been 21 suspected, 20 probable and three confirmed cases of Ebola between 4 April and 15 May, according to reports by theAssociated Press.
The ultimate fear now is if the virus, which can be fatal in up to 90 per cent of cases, were to spread to Kinshasa, a city that is home to almost 10 million people, many of whom live in slums with poor sanitation. It is an hours flight from Mbandaka
Mr Salama had told reporters on Thursday: Were certainly not trying to cause any panic in the national or international community.
What were saying though is that urban Ebola is very different phenomenon to rural Ebola because we know that people in urban areas can have far more contacts so that means that urban Ebola can result in an exponential increase in cases in a way that rural Ebola struggles to do.
Health teams are now monitoring more than 500 people who may have come in contact with infected individuals.
They say they are now better prepared to deal with the outbreak, compared to when a major outbreak killed more than 11,000 people across west Africa between 2014 to 2016, with more than 28,000 confirmed, probable and suspected cases.
A vaccine, which was tested during the previous outbreak, will be sent out and given to those who may have come into contact with the disease.
The organisation has already sent 4,300 doses to Kinshasa and is now sending 7,540 more doses to the region, claiming this should be enough to treat 50 rings of 150 people.
The WHOs ring vaccination method involves treatingthose who may have contacted those feared to be infected, their contacts and frontline health workers.
Last time, thousands died from the disease in countries including Liberia, Sierra Leone and Guinea and Nigeria.
Those infected included a number of British health workers including nurse Pauline Rafferty, who made a full recovery.
The virus can cause symptoms including vomiting, diarrhoea, muscle pain, headache, bleeding and a high temperature and can be fatal.
There is currently no licensed treatment for the disease, which is spread through contact with an infected person who has symptoms, through their bodily fluids and through handling raw or undercooked bushmeat.
A WHO emergency committee will meet tonight to decide if the outbreak is a public health emergency of international concern and how best to deal with it.
The global risk remains low.
The Foreign Office has not yet issued new advice on travel to the region, but have been contacted by The Independent for comment.
The NHS issued advice following the previous outbreak which includes to avoid physical contact with anyone who has possible symptoms of an infection and washing hands frequently with soap or failing that, rubbing them with alcohol.
It also advises not handling dead animals or raw meat, not eating bushmeat and making sure fruit and vegetables are washed and peeled before eating.
The Centers for Disease Control and Prevention in America has echoed the NHS advice and added that any travellers who experience symptoms or who have had contact with someone who has over the past 21 days should seek medical help immediately.
Agencies contributed to this report.