The World Health Organization (WHO) has warned of a yellow fever outbreak in Ethiopia.

The number of suspected cases has increased from three reported on 3 March to 85 on 6 April.

Eight of the suspected cases have tested positive.

Vaccination has since been reactivated but the WHO is concerned about the outbreak in cases with no travel history.

"The risk at national level is assessed as high. The current outbreak in Gurage Zone, SNNP region shows rapid amplification of a yellow fever outbreak in a rural area," the WHO said.

"In the context of virtually no population immunity, the high number of suspect cases reported over a short time period is of high concern."

Ethiopia has been running yellow fever vaccination programmes targeting people living in hot spots.

What is yellow fever?

• Caused by a virus that is transmitted to humans by mosquitoes
• Difficult to diagnose and often confused with other diseases or fevers
• Presence of yellow fever antibodies can be detected by blood tests
• Most people recover after the first phase of infection that usually involves fever, muscle and back pain, headache, shivers, loss of appetite, and nausea or vomiting
• About 15% of people face a second, more serious phase involving high fever, jaundice, bleeding and deteriorating kidney function
• Half of those who enter the "toxic" phase usually die within 10 to 14 days The rest recover