Is dengue emerging as a major public health problem?
OBJECTIVE
Diagnosis of dengue infection is easily and best accomplished by demonstration of specific IgM antibodies in blood. We analyzed retrospectively the dengue IgM seropositivity available for samples obtained over a period of five year (1999-2003) from patients with suspected dengue fever (DF)-like illness to investigate whether there was an overall increase in the dengue IgM prevalence over this period.


METHODS
Serum samples from a total of 1426 individuals (suspected dengue cases) obtained over five year were tested for dengue specific IgM antibodies. Of the 1426 patients, 693 were adults (>15 yr) and 694 children (<15 yr) (excluding 39 individuals whose age was not known). There were 807 males and 610 females (excluding 9 individuals whose status on sex was unknown).


RESULTS
A total of 423 (29.7%) samples were positive for dengue IgM over the five year period. Overall, there was a significant increase in the percentage of dengue IgM positive individuals over the this period (P<0.001). When the individuals were grouped into children (<15 yr) and adults (>15 yr), a significant increase in the number of dengue IgM positive individuals was noticed only in children (P<0.001) and not in adults. When the individuals were grouped into males and females, a significant increase in the number of dengue IgM positive individuals was noticed in both the sexes (P<0.03). Month-wise analysis of the dengue IgM positivity rates indicated the year-wide occurrence of dengue. A total of 158 (41%) of the dengue IgM positive individuals showed positivity for dengue IgG also suggestive of a secondary heterotypic infection.


CONCLUSIONS
The overall significant increase in dengue IgM seropositivity among the suspected cases indicates an increase in dengue virus activity, raising the question whether dengue is emerging/re-emerging as a major health problem in southern India. Increase in probable secondary infection (as evidenced by dual positivity for dengue IgM and IgG) seen in this study is also a point of concern. Such an increase especially in a country like ours where multiple serotypes are prevalent, raises concern over probable increase in the incidences of the more serious DHF/DSS. As this report could well be an underestimate of true incidence, the alarming increase observed in 2003, may be a warning/indication of epidemics to come soon that merits serious consideration.
Vijayakumar
T S
TS
Department of Clinical Virology, Christian Medical College, Vellore, India.
Chandy
Sara
S
Sathish
Narayanan
N
Abraham
Mary
M
Abraham
Priya
P
Sridharan
Gopalan
G
D000293:Adolescent; D000328:Adult; D002648:Child; D003715:Dengue / Q000453:epidemiology*; D006801:Humans; D007194:India / Q000453:epidemiology; D011634:Public Health