While non-reporting by certain member countries has, to some extent, contributed to the observed decline, this epidemiological pattern of reduced morbidity is typical of the dry season months of January through April. The effect of changing weather and climatic conditions, such as global warming and the El Nino /La Nina phenomena, on the environment and bionomics of the Aedes aegypti mosquito, needs to be closely monitored.

A review of CAREC's laboratory data for the first quarter of 1999 indicates that of 208 patients referred from 14 CAREC member countries [CMCs] for laboratory confirmation of dengue fever, 35 or 16.8% were confirmed as having dengue fever. Dengue virus type 2 activity was identified in Grenada as well as in Trinidad and Tobago, while both types 2 and 3 were documented in Barbados. Dengue virus type 3 activity was also observed in St.Christopher/Nevis and Aruba [Table2].

A review of the data being generated by CAREC member countries through the Measles Elimination Surveillance System [MESS] indicates that over the period under review, 8 patients referred with febrile rash illness from three CMCs, namely, Grenada, Guyana and Suriname, were confirmed as having dengue fever by IgM serology.

In February 1999, CAREC was notified of an outbreak of dengue fever in Aruba. Dengue virus type 3 was confirmed as the aetiologic agent by the National Laboratory Authorities in Venezuela.

Since the introduction of DEN-3 into the Americas in 1994, the presence of this specific aetiologic agent has now been confirmed in five CMCs, namely, Belize, Jamaica, Barbados, St. Christopher/Nevis and Aruba.

There is urgent need for improved communication at the country level between the epidemiologist, the laboratory director and the EPI Manager in order to ensure that final national figures do include data from the different arms of the surveillance system. For example, confirmations of dengue fever generated via the MESS must be consolidated with the dengue data from other sources. Additionally, the national Vector Control Managers must also be apprised of these findings.

Among non-CAREC members, no suspected cases of measles were notified from Guadeloupe during the first quarter of 1999, while 39 of 158 patients referred to CAREC's laboratories from the Dominican Republic were diagnosed as positive by IgM serology.

Although no cases of rubella were notified through the national weekly communicable disease reporting system, rubella virus circulation was documented in Belize and Suriname, where 2 and 3 cases, respectively, were confirmed through the MESS system. Cases of rubella were also identified in the Dominican Republic as 38 of 119 patients referred were diagnosed as positive by IgM serology.

While increased influenza morbidity was recorded in North America and Europe during the first quarter of 1999 [WHO Weekly Epidemiological Reports; US Centers for Disease Control & Prevention: Influenza Activity Report for the 1998/99 season], a similar epidemiological trend has not been observed for the sub-region as a whole. Our data indicate that during the first quarter of the current year, 7,138 cases of influenza were notified to CAREC's Epidemiology Division from 16 member countries as compared with 20,421 cases from 19 members during the corresponding period of 1998. To date, no data have been received from Suriname, Guyana or St. Vincent & the Grenadines, which together had accounted for nearly 40% of the reported 1998 morbidity. Of the 16 member countries reporting to date, only Jamaica, Trinidad and Tobago and the British Virgin Islands, have actually notified fewer influenza cases in 1999 than in 1998.

From an individual country perspective, however, it is of interest to note that higher influenza incidence rates were recorded in eight CMCs during 1999 as compared with the 1998 situation. Some of the highest rates were observed in the Turks & Caicos Islands [3,707 cases per 100,000 population]; in Bermuda [2,370 cases per 100,000 population]; and the Cayman Islands [1,331 cases per 100,000 population] [Figure2]. It is possible that the high morbidity notified from these three CMCs may have been linked to the occurrence, earlier this year, of influenza outbreaks aboard a number of cruiseships with Caribbean destinations [Carec Fax Alert 1/99]. The US Centre's for Disease Control and Prevention reported that between October 1998 and February 1999 nearly 80% of the influenza virus isolates recovered in the United States were identified as type A, with H3N1 strains being the most common subtype. No information on circulating influenza virus types is available from CAREC member countries.

In Guadeloupe and Martinique, influenza transmission patterns are linked to those in mainland France. In these two countries, data on influenza morbidity are collected both through a specialised regional group as well as a general sentinel physician network, in which cases are reported and clinical specimens are obtained for laboratory investigation at a reference centre located at the Institute Pasteur in Guyane. A dramatic increase in the number of reported cases was observed in Martinique, subsequent to the introduction of influenza type A [predominantly subtype H3N1] in January, 1999 [Figure3].

During the period under review, 12 confirmed cases of meningococcal infection were reported to CAREC’s Epidemiology Division, 10 of which were from Trinidad and Tobago, with one case each from Jamaica and the Cayman Islands.

Between September 1998 and February 1999, an outbreak of meningococcal infection occurred in Trinidad and Tobago [Figure 4]. CAREC's laboratories identified and serotyped isolates from 12 cases as Neisseria meningitidis Group B, while one was characterised as a group A meningococcus. Sub-typing analyses undertaken at the Laboratory Centre for Disease Control in Canada indicated that nine of the group B isolates possessed identical antigenic markers, serotype 15, subtype P1.7, 16, electrophoretic type [ET] 5. It should be noted that this specific strain has been reportedly linked to more virulent infections in France and Great Britain during the 1990s. The single isolate from the Cayman Islands also possessed the same antigenic markers.

Identification and sero-grouping of Neisseria meningitidis must be undertaken rapidly and reliably in order to implement timely prevention and control, aimed at reducing the occurrence of secondary cases. Such strategies may include both chemoprophylaxis as well as vaccination [for sero-groups A and C]. There are two objectives to the initiation of prophylactic measures and these are the prevention of secondary cases among contacts and the prevention of the evolution of epidemics. Prophylactic measures are more effective when they are implemented rapidly and applied to target groups.

A contact must be clearly defined as follows:

During the months of January and February 1999, an increase in the number of jaundice cases was reported in the Cayo health district of Belize, which borders Guatemala. Ten cases of jaundice had been reported among children between the ages of 4 and 12 years and one death was recorded on January 10, in an 11 year old boy who was diagnosed with hepatitis B. This child had died at the Melchor hospital in Guatemala. During the same period, 2 cases of jaundice were notified among adults.

A joint team, consisting of the national epidemiologist and public health nurses from the Ministry of Health in Belize and a CAREC epidemiologist, conducted an epidemiologic investigation of five clusters of suspected cases of leptospirosis in the Cayo district. These cases were interviewed and through active surveillance a further 6 were identified, resulting in a total of 16 cases among children, aged 4 to 12 years. These patients exhibited very mild clinical symptoms, which were compatible with the case definition for hepatitis A. Five cases, from 3 of the 5 clusters, were confirmed as viral hepatitis A infections by IgM serology [evidence of a recent infection]. The two jaundiced adults did not meet the case definition for hepatitis A. One was a confirmed case of sickle cell anaemia and the symptoms of the other were more closely compatible with the case definition for leptospirosis.

In summary, an outbreak of viral hepatitis A was confirmed among children, aged 4 to 12 years, from 5 different clusters in the Cayo district. While there was no statistical evidence to link any specific exposure to the occurrence of this outbreak, transmission through water in frozen drinks was highly probable.

The importance of obtaining data from patients on recent travel history cannot be overemphasised, as the potential opportunities for importation of exotic diseases, such as yellow fever, and other diseases, which may have already been eliminated in our sub-region, such as poliomyelitis, are rapidly escalating. Increased holiday and business travel, eco-tourism safaris, religious pilgrimages and expanding economic activity into hitherto inaccessible ecologic and geographic zones, such as gold mining in parts of the Amazon Basin, have greatly expanded the potential for importation of infectious pathogens.

At the recently concluded Technical Advisory Group Meeting on Immunisation in the Americas, it was reported by a Canadian presenter that polio virus had been isolated from a young child presenting with gastroenteritis, upon return from vacation in India. This child had been vaccinated with injectible polio vaccine in accordance with national Canadian guidelines.

In our sub-region, where there is limited national diagnostic capability in the area of virology, it is very likely no testing would have been undertaken for viral pathogens, even though routine examinations would have been conducted to identify possible bacterial and/or parasitic agents. Hence, given the same scenario, the occurrence of an imported poliovirus infection would, most likely, have been missed. The provision of a travel history together with knowledge of existing epidemiologic situations would certainly facilitate broader testing strategies by national and regional laboratories.