UNITED NATIONS (AP) — Nobody likes mosquitoes, and the World Health Organization blames them for an array of diseases that kill a million people each year and threaten the health of half the world's people.

On World Health Day, WHO's executive director Jacob Kumaresan took aim at mosquitoes, flies, ticks and other biting bugs that spread malaria, dengue fever, yellow fever, Chagas disease and leishmaniasis for causing "a silent disaster" worldwide. Most victims survive, he said, but often they suffer lifelong disability.

Kumaresan said Monday that warming temperatures around the world have helped spread diseases to new countries. He said dengue fever, notoriously known as "bone-break disease" for the pain it causes, used to be confined to 10 countries but now has spread to about a hundred, even as far as China and the United States, in south Florida.

Dengue fever incapacitates the victim for at least two weeks, and sometimes three weeks if he or she is hospitalized, a huge economic burden on the family and society in general, he said. Dengue is also being spread by the much more free movement of goods and people in the modern economy, he added.

Dengue fever has no current treatment or cure, and can only be treated symptomatically. Kumaresan said vaccines were being researched.

The WHO chief also said malaria has spread to Ethiopia's highlands, where 10 years ago it was too cool for the virus to thrive.

Among the problems in fighting these problems are that common insecticides are losing their potency as bugs adapt, and many diseases are becoming drug-resistant, notably malaria.

Kumaresan said several relatively low-cost techniques to combat bug-borne diseases include vaccination, insect-proof bed nets, insecticides and programs to drain stagnant pools of water that mosquitoes use as breeding grounds.