The Incidence of this fever is variable and depends on the geographical region and the density of mosquito-borne
diseases in a region.
The worldwide incidence is estimated to be 50 to 100 million cases of dengue fever (DF) and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year.
DHF is more serious and the fatality rate is about 5%.
Children younger than 15 years comprise 90% of DHF subjects in the world. DHF can affect both adults and children.
Poor surveillance system in India makes it difficult to know the exact incidence of the epidemic in the country. There have been reports regularly in medical literature from various hospitals. Between September 2001 and January 2002, during the epidemic of dengue in Chennai, Tamil Nadu, India nearly 800 cases were reported to the health system.
The world's largest known epidemic occurred in Cuba in 1981. More than 116,000 persons were hospitalized with as many as 11,000 cases reported in one single day.
In the year 1995, it is estimated that in America alone there were 250,000 cases of Dengue Fever and about 7,000 cases of DHF.
Interestingly the El Niño cycle maybe related to diseases transmitted by mosquitoes, such as malaria
and dengue. Mosquito breeding to some extent depends on the weather conditions. If the humidity is high or when the droughts occurs and rivers beds dry up leaving small stagnant pools, the mosquitoes breed easily. Again in dry climates, a spell of heavy rainfall can create puddles and this provides good breeding conditions for mosquitoes. Few interesting facts about El Niño are as follows:
El Niño,an oceanic current of warm water, usually occurs once in about 2-7 years and effects lasts for 12 to 18 months.
During a typical El Niño cycle in the Asian region, the monsoon is weakened and this brings summer drought to north-west and central regions of India with associated heavy rainfall in the north-east.
The regions of the world where El Niño has a strong effect on climate conditions include - southern Africa, parts of South America and South-east Asia. Incidently, these regions also have some of the poorest countries in the world .