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COMMUNICABLE DISEASES FEEDBACK REPORT
Reporting period: Epidemiologic Weeks 13 - 24 of 1999
A Review of Selected Communicable Diseases
Dengue Fever
The low incidence of reported dengue fever morbidity observed during the first 12 weeks of 1999 continued during the second quarter, when 113 cases were reported to CAREC’s Epidemiology Division, as compared with 327 cases for the corresponding period in 1998
[Figure
1; Table 1]. During the period under review, 99 cases of dengue fever (representing 87.6% of total notifications for the period) were recorded in Trinidad and Tobago, in addition to 8 cases of
DHF/DSS cases (representing all of the reported cases for the period). Cases of dengue fever were also notified from Barbados (6), Belize (3), St. Vincent and the Grenadines (3), The Bahamas (1) and Jamaica (1). A DEN-3 outbreak, which was reported from Aruba during the first quarter of 1999, had subsided by week number 13.
Data from CAREC’s Laboratory, for January to June 1999, has confirmed the continued circulation of DEN-1, DEN-2 and DEN-3 in CAREC member countries, though at low levels. These specific serotypes accounted for 10%, 70% and 20% of the total viral confirmations, respectively.
A similar low level of reported dengue fever incidence was also noted in the French Departments of the Americas during the first and second quarters of 1999. Only sporadic cases of IgM positives were detected through the Physician Based Surveillance System in Martinique
[Figure 2] and Guadeloupe, while the Pasteur Institute of Cayenne (French National Reference
Centre) confirmed DEN-1 isolates in Martinique and DEN-2 isolates in French Guiana during the period under review.
Trends in reported dengue fever morbidity should be closely monitored as the rainy season unfolds during the remaining months of the year. Most of our member countries have experienced past infections with DEN-1, DEN-2 and DEN-4 viruses, and further, DEN-3 has been circulating in Barbados, St. Christopher/Nevis and Aruba. Given this current situation, there is a need to be particularly vigilant as regards the potential occurrence of cases of
DHF/DSS.
Outbreak of DEN-3 in Aruba
During the first quarter of 1999, an outbreak of DEN-3 occurred in Aruba. Beginning in late December 1998 through epidemiologic week number 13, 136 cases of dengue fever and dengue haemorrhagic fever were notified by the Department of Public Health. Forty four percent of these cases were laboratory confirmed and no deaths were recorded. Clinical specimens were referred to the National Institute of Hygiene in Caracas, Venezuela, and DEN-3 was confirmed as the aetiologic agent. Although peak transmission was observed in January, the epidemic curve had declined dramatically by mid-February, following the implementation of aggressive adulticiding and source reduction measures
[Figure 3]
No obvious link was identified with the dengue viral activity on the mainland, as only DEN-1, DEN-2 and DEN-4 serotypes have been identified in Venezuela since 1998. This outbreak of dengue fever is the third to have occurred in Aruba during the past 15 years. An outbreak of DEN-1, with an estimated attack rate of 25%, was recorded in 1984-85, while a DEN-2 outbreak was reported in 1995.
Influenza
During the period under review, 6,498 cases of influenza were reported to CAREC’s Epidemiology Division as compared with 13,955 cases notified during the corresponding period in 1998. This greater than fifty percent decrease in the number of reported cases was mostly due to non-reporting from Suriname, which had accounted for 37.6% of the influenza notifications to CAREC during the second quarter of 1998.
During the second quarter of 1999, there was a decline in reported influenza morbidity for the region as a whole [Figure 4], a pattern which was co-incident with the end of the influenza season in the USA and in the European Union. During this period, however, an extensive outbreak was reported in the southern cone countries of Brazil, Uruguay, Argentina and Chile
[WHO's FLUNET Database].
The influenza outbreaks that occurred during the first quarter of 1999 in Bermuda, the Turks & Caicos Islands and the Cayman Islands had subsided by April
[CAREC-CDFR 1/99].
In 1999, Jamaica was the only CAREC member country to report on influenza virus types, with cases of influenza A (H3N2) and influenza B being diagnosed
[WHO's Weekly Epidemiologic Report: No. 24, June 18, 1999] In the French islands of Martinique and Guadeloupe, influenza activity, which appears to be linked to patterns in Europe, subsided during the second quarter
[Figure 5]. The Pasteur Institute of Cayenne (regional reference laboratory) reported that 75% of the isolates during the season were type A.
The EID Corner
Malaria
Malaria is considered to have been eradicated from the French West Indies for over 30 years. In Guadeloupe, by the 1940s, most of the foci were located on the leeward coast, with seasonal transmission of
Plasmodium falciparum occurring at altitudes of less than 400 meters. Anopheles aquasalis and
Anopheles argyritarsis were the vectors involved in this cycle. A campaign of DDT intra-domiciliary spraying together with community-based distribution of
chloroquine, resulted in the successful elimination of autochthonous malaria by the end of the 1950s.
Apart from regularly reported imported cases, most of them from Haiti, 3 cases of malaria linked to tourists who had travelled to Guadeloupe were documented within the last ten years (2 of
P. falciparum and 1 unspecified). Given that a reservoir of P. falciparum gametocytes exists in the Haitian community and that competent vectors are present in Guadeloupe, a recently published paper considered the possibility of the re-emergence of autochthonous malaria transmission
[Med. Trop., Vol 59, 1, 1999].
During the last ten years most of the cases detected in the Caribbean islands (excluding Haiti and the Dominican Republic), have been imported. However, some outbreaks have been reported in previously malaria-free countries:
 | P. vivax in Trinidad, 1991
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| P. malariae in Trinidad, 1995
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| P. falciparum / P. vivax in the Cayman Islands, 1997, and
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| P. falciparum in the Bahamas, 1998. |
Endemic transmission of malaria involving P. vivax and
P. falciparum
occurs in all of the mainland CAREC member countries (Belize, Guyana, Suriname). In Haiti and the Dominican Republic, however, where transmission is ongoing,
P. falciparum accounts for most of the malaria cases.
A competent vector exists in all the Caribbean islands in that the
Anopheles albimanus distribution ranges from the Greater Antilles in the north-west, running down the chain of islands, to the Leeward islands where there is an overlap with
Anopheles aquasalis.
Due to the presence of competent Anopheles species and the high migration of infected persons from endemic areas within the Caribbean, the re-introduction of malaria is a permanent threat for malaria-free countries.
Dr. M. J Lewis, Dr. E. Boisson, Dr. S. Aldighieri and Team
September 24, 1999
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