The following study was intended to evaluate the occurrence of typical signs and symptoms in the cases of classic dengue and hemorrhagic dengue fever, during the 2001-2002 epidemic in the city of Rio de Janeiro. The authors reviewed 155,242 cases notified to the Information System of Notification Diseases, from January/2001 to June/2002: 81,327 cases were classified as classic dengue and 958 as hemorrhagic dengue fever, with a total of 60 deaths. Common symptoms, such as fever, headache, prostration, myalgia, nausea and retro-orbital pain, had a high incidence in both classic and hemorrhagic dengue fever. On the other hand, hemorrhagic signs and other signs of severe disease, such as shock, gastrointestinal bleeding, petechiae, epistaxis, abdominal pain and pleural effusion, were strongly associated to hemorrhagic dengue fever. Besides, the occurrence of death was 34.8 times higher in hemorrhagic dengue fever than in classic dengue (OR = 34.8; CI 19.7-61.3).

The authors evaluated clinical and epidemiological differences among the serotypes of dengue in Rio de Janeiro's 2001-2002 outbreak of the disease. Out of 362 cases that had viral isolation samples, notified by the Information System for Notification Diseases (SINAN), from January/2001 to June/2002, 62 were caused by serotype 1,62 by serotype 2 and 238 by serotype 3. In comparison with serotype 2, an individual infected by serotype 3 had a 6.07 times higher chance (OR = 6.07; CI: 1.10-43.97) of presenting shock and a 3.55 times higher chance (OR = 3.55; CI: 1.28-9.97) of developing exanthema. When compared to serotype 1, serotype 3 had a 3.06 times higher chance (OR = 3.06; CI: 0.99-9.66) of causing abdominal pain and a 3.61 times higher chance of exanthema (OR = 3.61; CI: 1.16-11.51). It was found that individuals infected by serotype 3 of the virus presented signs indicating a more severe disease.