After World War II ended in 1945, the world was in rough shape. Millions of people were sick, and many countries had lost their hospitals and doctors. Diseases like malaria, tuberculosis, and smallpox were spreading fast, especially in poor countries that had no way to fight them. On April 7, 1948, the United Nations created the World Health Organization -- the WHO -- to tackle this crisis. The WHO's first major mission was fighting malaria, a disease spread by mosquitoes that killed millions of people every year. The organization sent teams of doctors and scientists to countries across Africa, Asia, and South America. They sprayed areas to kill mosquitoes, handed out medicine, and trained local health workers. The WHO's greatest achievement came in 1980, when it announced that smallpox had been completely wiped out. No other disease in history has been eliminated by human effort. It took over a decade of work across every continent, with health workers vaccinating people in remote villages, crowded cities. War zones. The program required cooperation between countries that normally did not get along. Even the United States and the Soviet Union worked together. Today, the WHO works in over 150 countries. It helps fight diseases, makes rules about food safety, and responds to emergencies like outbreaks of new illnesses. Every year on April 7, the world celebrates World Health Day. It reminds people that health is something every person deserves.