In the African country of Ethiopia, 10 people were killed by yellow fever, since August, at least 35 have been infected.
The tropical disease is caused by a virus that is spread by mosquitoes and is most commonly found in Africa and America.
Ethiopia's recent outbreak is in the Wolaita Zone in the southwest of the country, due to a patient who fell ill on 21 August.
The World Health Organization is sending 1.45 million vaccines from its supply to the country, in a desperate attempt to halt the spread of the virus.
Yellow Fever, a deadly mosquito-borne virus, is reported to have infected 35 people in Ethiopia's southwestern Wolaita zone since an outbreak was triggered when someone contracted an infection in August this year
In a WHO report, officials said, "This outbreak is worrying as the population in Ethiopia is very prone to yellow fever due to lack of exposure and lack of vaccines."
Western travelers can easily be vaccinated against yellow fever before traveling to countries where the infection is detected. However, jabs are not routinely issued.
Symptoms of the infection include fever, headache, muscle aches, vomiting and fatigue. Every year, an estimated 30,000 people die worldwide.
The World Health Organization said earlier this year that yellow fever is a "major" threat to humanity, but not "urgent."
Around 200,000 people are infected with the virus every year and can quickly spread from non-vaccinated populations through mosquitoes.
WHAT IS YELLOW FEVER?
Yellow fever is a serious viral infection that often occurs in tropical and subtropical areas.
The mosquito-borne virus usually kills up to eight percent of the people it attacks.
Nearly 200,000 cases and 30,000 fatalities are reported worldwide each year.
The World Health Organization said last month that yellow fever is a "major" threat to humanity – but not "urgent."
Symptoms include fever, severe headache, muscle aches, nausea, vomiting, and tiredness. But they can move quickly.
It can not be caught directly by other people.
Ethiopia's outbreak occurs in a region called Southern Nations, Nationalities and Peoples (SNNP).
In October, 31,000 people were vaccinated in the Offa district of the region in response to the outbreak, and since then there have been no new cases.
However, the WHO warns that there is a risk of the infection spreading, also due to armed conflicts in the region.
Ethiopia is located in the geographical "Yellow Belt", which includes many Central African and Central and South American countries, and had frequent outbreaks until the 1960s.
According to the WHO, there were no cases in the SNNP after the 1960s until an outbreak of 143 cases in 2013.
Ethiopia plans to routinely vaccinate children against yellow fever from 2020 onwards.
The Republic of Congo, a country in West Africa, faced a similar problem earlier this year when officials said that more than 180 people had yellow fever.
An epidemic was declared there on 24 August and officials promised to start a free national vaccination campaign.