GENEVA (Reuters) - The World Health Organization is releasing more than a million doses of yellow fever vaccine from its emergency stockpile after the deadly mosquito-borne disease killed 10 people in southwestern Ethiopia, a WHO report said on Monday.

The outbreak was confirmed in Wolaita Zone of the Southern Nations, Nationalities, and Peoples’ Region and has been traced back to a patient who fell ill on Aug. 21. It has caused 35 suspected cases of the disease.

“This outbreak is of concern since the population of Ethiopia is highly susceptible to yellow fever due to absence of recent exposure and lack of large-scale immunization,” the WHO report said.

Symptoms include fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue, and although only a small proportion of patients who contract the virus develop severe symptoms, about half of those die within seven to 10 days.

All the confirmed cases came from Offa Woreda district, and there have been no more confirmed cases since an immediate reactive vaccination campaign was conducted there in mid-October, reaching around 31,000 people.

However, the WHO said there was a risk of further spread of the disease, partly because of conflict in the region, and it was releasing 1.45 million doses of vaccine for a mass campaign that needed to take place “without further delay”.

Ethiopia, the home country of WHO Director-General Tedros Adhanom Ghebreyesus, is within the geographic “yellow fever belt” and had frequent outbreaks until the 1960s, but no more until 143 cases were confirmed in the SNNP region in 2013, the weekly report said.

The introduction of yellow fever vaccination into routine immunization in Ethiopia is planned for 2020.