Reported cases of measles worldwide have nearly tripled in the first half of 2019, compared to the same time frame last year, the World Health Organization (WHO) reported on Monday. 

Overall, there were 353,236 last year, while this year, 364,808 cases of measles have already been reported so far, a massive jump from the 129,239 cases recorded in the first half of 2018. Health experts remain alarmed as numbers have continuously climbed since 2016, now reaching the highest figures since 2006.

While the number of reported cases is astonishingly high, it is believed that the number of measles cases globally is actually much higher, as WHO estimates that more than 90% of cases go unreported. 

Measles is a highly infectious airborne virus, manifesting in symptoms such as high fever, cough, and rashes within seven to 14 days of contact with an infected person. In serious cases, measles can be deadly. 

Scientists have developed a measles vaccine, rendered effective by two doses, that can prevent humans from contracting the disease. However, WHO said on Monday that many people are not being vaccinated due to conflict, displacement, low awareness or misinformation about vaccines, and lack of access. The most popular reasons for missing vaccinations vary based on conditions in different countries and communities.

Read More: Germany Considers €2,500 Fine for Kids Not Vaccinated Against Measles

The countries with the highest number of measles cases this year are the Democratic Republic of the Congo, Madagascar, and Ukraine. The disease currently continues to ravage countries including Angola, Cameroon, Chad, Kazakhstan, Nigeria, Philippines, South Sudan, Sudan, and Thailand. 

According to WHO, the African region has seen a spike of 900% in reported cases of measles, and the West Pacific region — which includes Japan, China, and Australia — is the second most-affected, with the number of cases increasing by 230% since the first half of 2018. 

The number of measles cases in the United States also reached its highest peak in 25 years, while Europe’s count for the first six months has already exceeded the nearly 85,000 cases reported during the entirety of last year. 

Though Madagascar is of the countries with the highest measles count, it is also an exemplary case study of how effective vaccinations can be in helping to eradicate the disease. Since implementing widespread emergency vaccination campaigns, the number of new measles cases in Madagascar has significantly dwindled in the last several months. 

However, low rates of vaccination persist in some regions of the world. There are still 23 countries which have not incorporated the second dose of the vaccine — which helps to ensure its effectiveness — in national protocol. Measles outbreaks are even festering in countries that have historically had high vaccination rates, due to disparities in the administration of the vaccine among communities, geographic areas, and age groups. 

Read More: Largest Measles Outbreak in Madagascar's History Kills 1,200

According to WHO and UNICEF, approximately 20 million children were left vulnerable to the disease in 2018, receiving neither of the two doses of the vaccine. 

While the measles remains a rampant epidemic in some areas of the world, hope of eradicating the disease lies in efforts to raise awareness about the disease and educate affected populations on the safety and effectiveness of the preventative MMR vaccine.