Dengue hemorrhagic fever in Cuba, 1981: a retrospective seroepidemiologic study.

In Cuba, 2 epidemics of dengue virus occurred: 1 caused by DEN-1 in 1977 and 1 caused by DEN-2 in 1981. The latter was associated with cases of dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). To study viral risk factors for DHF/DSS, a retrospective seroepidemiological survey was conducted in Cerro, a densely populated district in Havana City. The prevalence of plaque reduction neutralizing antibodies to DEN-1 and DEN-2 viruses was measured in 1,295 individuals (children and adults). Of these, 43.7% were immune to DEN-1 virus and 23.6% to DEN-2 virus. Of those individuals who were immune, 26.1% were immune to DEN-1 virus only, 6% to DEN-2 virus only, and 17.6% to both viruses. The DEN-2 virus infection rate in DEN-1 immune individuals was 3.8 times higher than in non-immune individuals. The 5 DHF/DSS cases in the sample had evidence of DEN-1 virus plus DEN-2 virus infections. Three were children and 2 were young adults. No cases were found in individuals infected with DEN-1 virus or DEN-2 virus only. Children infected by DEN-1 virus followed by DEN-2 virus had a high risk of acquiring DHF/DSS. Blacks and whites were equally infected with DEN-1 and DEN-2 viruses.

Why dengue haemorrhagic fever in Cuba? 1. Individual risk factors for dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS).

During the dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) epidemic in Cuba in 1981, we identified some individual risk factors for the development of the severe clinical picture or for the fatal outcome of the disease. The percentage of secondary infection in 3 groups of patients with DHF/DSS was between 95 and 98.3 and it is concluded that secondary infection is an important, but not the only, condition for the development of DHF/DSS. An analysis of these 3 groups of patients and a fourth group of fatal cases showed that chronic diseases such as bronchial asthma, diabetes mellitus and sickle cell anaemia were additional risk factors contributing significantly to the development of DHF/DSS. The study also revealed that race was an individual risk factor, since DHF/DSS was more prevalent in white than in black persons.

Why dengue haemorrhagic fever in Cuba? 2. An integral analysis.

The epidemiological factors present in Cuba in 1981, when the dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) epidemic occurred, were exceptional when compared to those of other countries in the region. Evidence is presented which demonstrates that virulence of the circulating strain is an important element in the analysis of an epidemic. Although the two current hypotheses to explain the occurrence of DHF/DSS epidemics are valid in well defined but different epidemiological situations, neither Halstead's hypothesis of secondary-type infection or Rosen's hypothesis of the role played by the virulence of the circulating strain can explain all cases. An integrated, multifactorial and unifying hypothesis is presented, which could be applied in different epidemiological situations. It is based mainly on an in-depth analysis of the literature and of the Cuban experience.

Dengue haemorrhagic fever in Cuba. I. Serological confirmation of clinical diagnosis.

Serological studies by the haemagglutinin inhibition test to confirm a clinical diagnosis of dengue were done on 406 patients during the dengue 2 epidemic in Cuba in 1981. 49% of the cases were serologically positive; of these 64% was classified as primary and 36% as secondary. The frequency of symptoms is described: the most frequent were fever, headache, malaise and vomiting. Haemorrhagic manifestations predominated significantly in the secondary cases. The white race and female sex were found to predominate in the positive cases.

Dengue haemorrhagic fever in Cuba. II. Clinical investigations.

Clinical and serological studies were carried out on 114 patients admitted to hospital in Havana, Cuba with Dengue Haemorrhagic Fever and Dengue Shock Syndrome (DHF/DSS). Serological confirmation of dengue was obtained in 90% of cases, with 5% of cases primary and 95% secondary. Fever, haemorrhagic manifestations, vomiting and headache were the most frequent signs and symptoms. Among haemorrhagic manifestations, petechiae and vaginal bleeding were reported in a larger number of patients. 21 patients presented shock and, of these, 20 were secondary infections. The disease appeared more frequently in white persons and in women. The aetiopathogenicity of the syndromes is discussed. 95% of the cases could be explained on the basis of the secondary infection hypothesis.

Dengue haemorrhagic fever/dengue shock syndrome: lessons from the Cuban epidemic, 1981.

Dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) is one of the principal causes of hospitalization and death among children in several south-east Asian countries. Also, in the Region of the Americas, there has been an increase in the frequency of dengue fever epidemics and in the number of cases of DHF/DSS. In 1981 an epidemic of dengue haemorrhagic fever occurred in Cuba and this suggests that there is a high risk that such epidemics could recur in the region. The article summarizes the main clinical, virological, and epidemiological data obtained during the outbreak, some of which are reported for the first time.