Polio has returned to Syria after a long absence, and other dangerous diseases are on the increase.
The World Health Organisation has recorded the first suspected outbreak of polio for 14 years in the country, provoking renewed alarm at the collapse of health care caused by civil war.
Doctors in Syria are also seeing a flare-up of typhoid, hepatitis and the flesh-eating parasite leishmaniasis, blamed partly on the inability to administer a proper vaccination programme and partly on poor living conditions and a much-reduced access to health care.
Some 22 people in the north-eastern province of Deir Ezzor are showing symptoms that are "very likely" to be polio, Oliver Rosenbawer, from the WHO Global Polio Eradication Initiative, told The Daily Telegraph.
"We still need final confirmation from a laboratory, but all the indicators show that this is polio," said Mr Rosenbawer.
For centuries, epidemics of polio, a highly infectious disease that invades the nervous system and can cause paralysis within hours, blighted countries across the globe, leaving hundreds of thousands of children and adults permanently incapacitated.
Vaccination programmes have dramatically reduced the number of cases, and the disease is now targeted for global eradication. The global number of cases has fallen from 350,000 in 1988 to 223 last year, according to the WHO.
Until this outbreak in Deir Ezzor, the last recorded case of polio in Syria was in 1999. "We are worried about the suspected outbreak," said Mr Rosenbawer.
"As long as there is polio in one place, countries around the world are at risk. The tragedy is that there is no cure; once you have polio, it is for life. So the only way is to tackle it is through vaccination."
Immunisation, already insufficiently widespread in Syria before the civil war, is almost impossible to carry out in Deir Ezzor and other parts of the country that are subjected to near constant shellfire and air strikes, or are rife with lawlessness and kidnappings.
A study by the WHO earlier this year found that at least 35 per cent of the country's public hospitals had been damaged or destroyed in the conflict and that in some areas, up to 70 per cent of health workers had fled.
In recent months the WHO has set up an "early warning and response system" designed to identify possible outbreaks of dangerous diseases within Syria, said Tarik Jasarevic, a spokesman.
"We have 291 public health providers in government and opposition-held areas reporting suspected diseases that we then investigate. This network has detected hepatitis A, leishmaniasis, typhoid and measles."
In war-riven Aleppo, the summer heat combined with streets filled with putrid, uncollected rubbish, allowed leishmaniasis to thrive.
Doctors recorded tens of thousand of cases of the tropical disease, transmitted by sand flies, that causes skin ulcers resembling leprosy.
The mass exodus of Syrian civilians fleeing the war is also increasing the risk of conveying diseases that had mostly been eradicated through vaccination back to neighbouring countries.
Meanwhile, nine Lebanese citizens who were kidnapped by rebel Syrian groups in May last year arrived back in Beirut on Saturday, after a hostage swap with two Turkish airline pilots who were held prisoner by gunmen in Lebanon.
Lebanon says the hostages were Shia pilgrims, but the rebel opposition accused them of being part of the Lebanese militia Hizbollah.