It begins as a fever, similar to a bad cold or flu. A headache soon emerges within a day or two, alongside agonising pains in the hands and feet. 

Within 24-hours, you might notice the pain spread up the arm, which soon turns numb.

This is the disturbing series of symptoms suffered by victims of the debilitating 'sloth fever' virus that has been reported in 19 people in Europe over the past two months, according to the European Center for Disease Control (ECDC).

Experts have raised the alarm about the potentially deadly disease — which originated in sloths — warning the spread could become 'unstoppable' due to the absence of vaccines.

MailOnline can now reveal three disturbing cases of the infection, which is spread by insect bites, in three Italian patients, as documented by the doctors who treated them. 

Five cases have so far been reported in Italy, as well as two in Germany and 12 in Spain. 

Outside of Europe, 8000 cases have been documented worldwide since January, mostly in South and Central America where the virus is more common. 

While experts say the virus is unlikely to 'take hold' in nations with cooler climates like Britain, it could become a problem for those travelling abroad.

'Climate change means infected insects have been detected as far as the South of France, where a lot of British people go on holiday,' says Dr Danny Altmann, a professor of Immunology at Imperial College. 

'Quite simply, people go abroad, pick up the virus and bring it back.  

'The virus is concerning for people living in the US as infected mosquitos have now reached the San Francisco region, and could spread further.'

The first European case was detailed by doctors at the Sacro Cuore hospital in Calabria, Southern Italy.  

The patient, a 45 year-old man, had recently travelled to the tropical Caribbean region — close to the South American nations from which the majority of cases have emerged. 

This includes Brazil, Bolivia, Peru, Columbia and Cuba. 

The man suffered flu-like symptoms, including high fever, headache, muscle and joint pain, the Italian medics reported. 

After other tests were performed to rule out underlying conditions, doctors tested for the 'sloth virus', known medically as Oropouche, using specialist blood tests. 

The patient is said to be under close medical monitoring, but his condition is 'stable'.

Another case involved a 'traveller' in their mid-twenties who had recently returned from a two week trip to Cuba — the doctors did not specify the patient's gender.

During the flight back home to Italy, the patient developed high fever as well as 'intense headache, nausea and diarrhoea'. 

The following day, the patient began experiencing intensive pain behind the eyes, as well as severe stiffness in the joints. 

The patient was tested for other, similar viruses including Dengue and Zika, with results reading negative. Blood tests for Oropouche were positive, and the patient is currently being monitored. 

A third patient, in their mid-fifties, had a history of high blood pressure, asthma and obesity and travelled to Cuba in May.

Two days after returning in early June, the patient developed a fever as well as pain behind the eyes and nausea. 

The symptoms had become so severe within three days that they visited the emergency room at the hospital of Forlì in Italy’s northern Emilia-Romagna region.

When doctors examined the patient, they noticed the left arm was slightly numb and round, red spots had appeared on the surface of the skin.

After tests for other viruses produced negative results, blood samples tested positive for Oropouche.

The doctors noted no damage to the internal organs and the abating of all symptoms apart from numbness in the arm within two weeks. 

The medics observed that the virus has an incubation period of three to 10 days — after which symptoms appear. They add that the fever is typically 'acute' for between two to four days before they vanish and then reappear seven to 10 days later.   

In severe cases, illness can result in meningitis, according to the NHS Travax website.

Although potentially deadly, the ECDC said fatal outcomes are extremely rare and recovery from the disease is common, usually within a week.

According to a report in the Lancet, on July 25 two deaths caused by Oropouche were reported for the first time in Brazil in two young women who had no other underlying health conditions.

The European authority is advising those travelling to affected areas, such as Brazil, Cuba, Peru and Columbia, to wear insect repellent and long-sleeved shirts and long trousers to reduce the risk of bites.

The strain behind the recent outbreak was first spotted in the tiny village of Oropouche, in Trinidad and Tobago, back in 1955.

Five years later, during the construction of the Belem-Brasilia highway, a sloth was found to be carrying Oropouche.

Within a year people in the area became ill with the virus and since there have been around 30 outbreaks, all centred in the Amazon basin.

The virus spreads in the jungle between sloths, birds and primates via infected midges and mosquitos. 

It is thought that these insects circulate in urban settings, where they can also infect humans. 

The increase in human cases is thought to be due to a number of factors including deforestation, which displaces animals such as sloths, as well as soaring temperatures that mean midges are flying further afield.