Mode of transmission
Dengue is transmitted by the bite of an infected mosquito, particularly Aedes aegypti- female mosquito. . This was first recognized by workers in Queensland early in the 20th century. Aedes aegypti breeds in fresh water and particularly in man made containers such as old tyres, pot plant holders, buckets and tree hollows in urban areas.
Aedes albopictus is a mosquito common in South East Asia and Papua New Guinea and can also be an important vector. Other Aedes species are involved in the enzootic monkey cycle
The principal vector mosquito, Ae. aegypti, prefers to feed on humans during the daytime and most frequently is found in or near human habitations. There are two peak periods of biting activity, in the morning for several hours after daybreak and in the late afternoon for several hours before dark. The mosquito may feed at any time during the day, however, especially indoors, in shady areas, or when it is overcast. Mosquito breeding sites include artificial water containers such as discarded tires, uncovered barrels, buckets, flower vases or pots, cans, and cisterns.
During the first months of 2007,over 16,000 cases have been reported in Paraguay, of which around 100 have been detected as DHF cases. This new epidemic is expected to continue in Paraguay for several months, given the forecast of continuous rain all through the summer. Ten deaths have also been reported, including recently a high ranking member of the Ministry of Health. The epidemic has been the root of a scandal in the Paraguayan Department of Health, where one official has resigned because he had approved the use of expired batches of insecticide to control the mosquito vectors of dengue.[10][11] The disease has propagated to Argentina (where it is not considered endemic), in almost all cases by people who recently arrived from Paraguay.[12] In the Brazilian state of Mato Grosso do Sul, which borders on Paraguay, the number of cases in March 2007 is estimated to be more than 45,000.[11] Epidemics in the states of Ceará, Pará, São Paulo, and Rio de Janeiro have taken the Brazilian national tally of cases this year to over 70,000, with upwards of 20 deaths. The proportion of cases registered as DHF is reported to be higher than in previous years