Figure 2. Americas countries with confirmed
dengue haemorrhagic fever/dengue shock
syndrome prior to 1981 (2A) and from
1981-1987 (2B)

00000000In 1985, a small and limited outbreak of dengue occurred in San Juan. DEN-1 was the predominant virus serotype, but DEN-2 and 4 were also isolated. Two cases of severe haemorrhagic disease were confirmed, both of them children. One DHF/DSS case that met the World Health Organization (WHO) case definition(13) was caused by DEN-1, and the other case (initially diagnosed as idiopathic purpuric thrombocytopenis) was caused by DEN-2 virus. In 1986, many cases of severe haemorrhagic disease were confirmed as dengue. Twenty-nine of the cases met WHO criteria for DHF/DSS, including three with a fatal outcome. Most of the severe cases in which the infecting virus serotype could be determined, including two that were fatal, were caused by DEN-4. DEN-2 virus was isolated from the other fatal case.

00000000This pattern of sporadic DHF/DSS continued in 1987and 1988 with smaller outbreaks. The DHF/DSS rate per 1000 confirmed dengue cases increased dramatically in 1986 and remained high(25-30) in 1987 and 1988. Most cases of severe haemorrhagic disease in Puerto Rico, including deaths, have occurred in children under the age of 15 years, but adult cases have also been documented. The data suggest that the pattern of severe haemorrhagic disease in Puerto Rico is evolving in a manner identical to that in South-East Asia. If true, the island is at high risk for a major epidemic of DHF/DSS