Image caption Medical facilities are often basic in rebel-held areas

The World Health Organization is warning of an increased risk of disease epidemics in Syria and neighbouring countries as summer approaches.

The WHO says outbreaks of diseases carried in water - specifically hepatitis, typhoid, cholera and dysentery - are inevitable, given the severe disruption to Syria's health system.

Cases of diarrhoea and hepatitis-A have more than doubled since January.

There have also been outbreaks of measles and typhoid.

We are anticipating a number of public health risks from water-borne diseases, specifically hepatitis, typhoid, cholera and dysentery Dr Jaouad Mahjour, Department for communicable diseases, WHO's regional office for the Eastern Mediterranean

According to the WHO, at least 35% of the country's public hospitals are out of service, and in some areas, up to 70% of the health workforce has fled.

Almost 4.25 million Syrians who have had to leave their homes are living in overcrowded, unsanitary conditions, with concerns about the provision of safe drinking water and safe sanitation.

"All the risk factors that enhance the transmission of communicable diseases in emergencies are present in the current crisis in Syria and its neighbouring countries," said Dr Jaouad Mahjour, director of the department for communicable diseases at the WHO's regional office for the Eastern Mediterranean.

"We are anticipating a number of public health risks from water-borne diseases, specifically hepatitis, typhoid, cholera and dysentery.

"Given the scale of population movement both inside Syria and across borders, together with deteriorating environmental health conditions, outbreaks are inevitable."

Vaccination problems

The WHO says cases of measles have reappeared in Syria, due to problems running national vaccination campaigns.

The number of confirmed cases of measles in the first quarter of 2013 reached 139, compared with no cases in the whole of 2010 and 2011, says the WHO.

There have also been reports of measles, tuberculosis and cutaneous leishmaniasis - a disease carried by insects - among displaced Syrians in Jordan, Lebanon, Iraq and Turkey.

"Jordan had previously reported zero cases of measles for three years, and was planning to officially declare that it was measles-free," said Dr Mahjour.

"The situation will deteriorate if prevention and control measures are not scaled up soon."