Yellow fever is a serious disease caused by a virus that is spread by mosquitos in tropical areas of Africa and South America.

Each year, Yellow fever causes about 200,000 infections and 30,000 deaths. About 90% of the cases occur in Africa. The disease is common in warm, tropical climates such as South America and Africa, but it is not found in Asia.

You may think that the number of people infected would be decreasing, but since the 1980s the number of yellow fever cases has unfortunately increased. This is believed to be due to the fact that more and more people are living in cities, that we are traveling more than before, and an increased climate impact.

Since there is no cure for the disease, preventive vaccination is a very important measure. Max Theiler successfully infected mice with a virus in the 1930s, which opened the door to more in-depth studies. When the virus was transferred between mice, a weakened form of the virus was created that gave monkeys immunity. In 1937, Theiler was able to develop an even weaker version of the virus. This version could be used as a vaccine for people.

Max Theiler was awarded the Nobel Prize in Physiology or Medicine in 1951. In his speech at the Nobel Banquet he said:

To have been considered worthy of receiving the Nobel Prize – the highest honor that any scientist can receive – gives me a feeling of great personal satisfaction. Such tangible evidence that my work has been considered of benefit to mankind is indeed very gratifying.

Read the speech here.