Varicella zoster in Guinea-Bissau: intensity of exposure and severity of infection.
OBJECTIVE
To describe the epidemiology of and risk factors for severe chickenpox in Guinea- Bissau.


METHODS
A prospective household study in a semiurban area of the capital. Severity was assessed by number of pox, fever response and presence of pneumonia. Severity was compared for the first case in a house, that is, the index case, and the secondary cases infected at home.


RESULTS
We identified 1539 cases of chickenpox. The median age was lower for boys and secondary cases (both P < 0.03); 44.6% of children were 1-4 years of age. The likely minimum interval between index and secondary cases was 10 days; most secondary cases occurred 14-17 days after the index case. The length of the incubation period was related to the intensity of exposure (P < 0.01). The number of pox was higher for secondary cases (P < 0.01) and was related to intensity of exposure (P < 0.01). Secondary cases had higher fever and more frequently pneumonia (relative risk, 2.17; 95% confidence interval, 1.54-3.08). Children with pneumonia were younger and had more pox. Nutritional status was not related to severity.


CONCLUSIONS
Age and intensity of exposure are important determinants for severity of chickenpox infection. The length of the incubation period depends on intensity of exposure, suggesting that the dose of infection might be important.
Poulsen
Anja
A
Projecto de Saude de Bandim, Guinea-Bissau, Statens Serum Institut, Copenhagen, Denmark. anja@dadlnet.dk
Cabral
Fernando
F
Nielsen
Jens
J
Roth
Adam
A
Lisse
Ida Maria
IM
Vestergaard
Bent Faber
BF
Aaby
Peter
P
D000293:Adolescent; D000328:Adult; D002644:Chickenpox / Q000150:complications / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003441:Crowding; D004196:Disease Outbreaks; D005260:Female; D005334:Fever / Q000821:virology; D006169:Guinea-Bissau / Q000453:epidemiology; D006562:Herpes Zoster / Q000453:epidemiology*; D006798:Housing; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009752:Nutritional Status; D011014:Pneumonia / Q000821:virology; D012307:Risk Factors; D012720:Severity of Illness Index