In a report released last week, the WHO wrote that the outbreak was "unprecedented" and "occurred in a context of poor performance of routine immunization".
This report recorded 300 deaths and 53,000 infections. The dramatic increase in this period is due to a more complete data collection in Madagascar, said a spokeswoman on Friday.
According to preliminary figures from the WHO, 229,000 cases of measles were reported worldwide in 2018, double the previous year. The WHO experts say that the actual number of cases will probably be much higher.
The former French colony of Madagascar has about 25 million inhabitants and is one of the 30 poorest countries in the world, according to the United Nations.