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Dengue on French St. Martin is starting to decline

Posted Mar 08 2010 12:00am

St. Martin

Dengue was on the decline in Week 1, 2010 compared to December 2009 when the French Side averaged 130 doctor visits of persons who were on suspicion of having contracted the disease.  The 100 cases the physicians saw in Week 1 placed French St. Martin above the epidemic threshold for that time of year.

The Positivity Rate of laboratory confirmations in Week 1 was, at 55%, the high-end of the 40-55% obtained in December ‘09.  The Cases seemed to be shared between Dengue 1, 2 and 4 like what obtained last year.

Of the 4 Laboratory Confirmed Cases treated at hospital on the French side, 3 Cases were for non-life threatening conditions while a fourth had to be transferred to Pointe-à-Pitre for more specialized care.

No part of French St. Martin was spared since this most recent Dengue event commenced in late November ‘09.  The greatest concentrations of infections have affected the neighbourhoods spanning Grand Case to Baie Orientale and Concordia.

French St. Martin, like Guadeloupe was in epidemic mode at the end of Week 1, 2010. (Sources: promedmail.org , invs.sante.fr )

Fast forward…

For the fifth consecutive week since early January, the number of cases clinically suggestive of Dengue seen by general practitioners on the French Side was stable, fluctuating around 100 cases per week.  Although much lower than what was observed at the end of December, that number was above par for this period.

However, the number of Confirmed Cases decreased for the second consecutive week.  Indeed, 11 cases of Dengue were biologically confirmed in Week 2010-05, as opposed to about 30 cases a week in early January.  This translates to 42% (11 positive samples of 26) Positivity Rate of samples taken for Week 5, a measurable sign that Dengue activity was slightly higher than the threshold for that time of the year.

Over the first fortnight of February (2010-06 and 07), the number of Suspected Dengue Cases had decreased by 30%-40% to 60-70 cases a week.  This drop is even more dramatic when compared to the peak epidemic period at the end of December when 200 cases were being clocked every week.  In spite of all this, Dengue on St. Martin is still higher than normal.

Although Confirmed Dengue Cases tend to vary from week to week, there was a marked decrease in the second week of February (2010-07).   Biologically confirmed cases dropped more than 75% to 7 cases a week compared to 16 cases the previous week (2010-06) and 30 cases weekly beginning in January – again well above normal.

The number of Confirmed Cases for the first two weeks of February may have decreased, but the Positivity Rate (50%) of specimens tested did not.

Three distinct serotypes, Dengue-1, Dengue-2 and Dengue-4, have been circulating on French St. Martin since October 2009.  Dengue-2, which was already in circulation from last season, accounted for the large majority (77% of samples) of cases. Dengue-1 (majority virus in 2008-09) also continues in circulation. Dengue-4 has not been identified since beginning of the epidemic in week 2009-49)

Of the 10 Confirmed Cases of Dengue recorded from December 2009, more than half or 7 of them were hospitalized (6 in January) with a severe form of the disease including 1 with Dengue Hemorrhagic Fever (DHF).

The location of Confirmed Cases showed that the distribution of the disease is all over French St. Martin. Concordia, Cul-de-sac, Mount Vernon and East Bay had the highest transmission rates in January.  Baie Nettle has been added to the list come February.

The decrease in the number of biologically confirmed cases during week 2010-05 proved then that the epidemiological situation was still in “epidemic phase”.  The continued decrease in the number of Clinical Cases over Week 06 and 07 indicates that the Dengue epidemic on St. Martin is on the decline. (Source: invs.sante.fr 1, invs.sante.fr 2)

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