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P Aaby

Publications and source records attributed to P Aaby.

At least 145 records · Page 8Linked to original sources
PubMed1992

Influence of cross-sex transmission on measles mortality in rural Senegal.

Previous studies of measles mortality in West Africa have shown a significantly higher case-fatality rate (CFR) among girls than among boys. This study aimed to find out whether the male/female difference in CFR is related to different risks for boys and girls of being infected as secondary rather than index cases and of transmission from someone of the same or the opposite sex. The study was conducted in Niakhar, a rural area of Senegal (population 24,000). All cases of measles reported between March, 1983, and December, 1986, were investigated to determine source of infection and pattern of transmission. For each case, the closest source of infection was judged the most likely. Death was attributed to measles if it occurred within 6 weeks of the onset of rash. Girls had a higher measles CFR than boys (53 deaths/722 cases [7.3%] vs 45/778 [5.8%]); the relative risk of death was 1.30 (95% confidence interval [CI] 0.89-1.90). Secondary cases infected by a child of the opposite sex had a 2.44 (1.48-4.02) times higher risk of death than did secondary cases infected by a child of the same sex. The risk of cross-sex transmission of infection was significantly greater for female than for male secondary cases (1.26 [1.09-1.47]). When this difference in risk of exposure to infection from the opposite sex was taken into account, the difference in risk of death between girls and boys disappeared (1.06 [0.66-1.69]). Within families, the CFR was higher in huts with 1 boy and 1 girl affected than in huts of either 2 boys or 2 girls affected (relative risk 2.16 [0.99-4.70]). Measles infection contracted from a person of the opposite sex is more severe. Variation in exposure may be an important determinant of sex differences in case fatality.

Adolescent↗
PubMed1992

Increased risk of death from measles in children with a sibling of opposite sex in Senegal.

OBJECTIVE: To examine whether contracting measles from a sibling of the opposite sex affects mortality. DESIGN: Prospective registration during 15-20 years of all births and deaths, including 243 measles related deaths. Measles infection was not registered; however, as in fatal cases measles was probably contracted from a maternal sibling the risk of dying during measles outbreaks was examined in families with two boys, two girls, or a boy and a girl. SETTING: 31 small villages in two rural areas of eastern Senegal. SUBJECTS: 766 children living in families with two children aged under 10 years during outbreaks of measles, 107 (14%) of whom died of measles. MAIN OUTCOME MEASURE: Deaths from measles, size of village, age and sex of maternal siblings. RESULTS: The interval between outbreaks in the same village was greater than 10 years. The risk of dying of measles was significantly related to age, increasing with the age difference between siblings and decreasing with the size of village. In a multiple logistic regression analysis adjusting for these background factors, children in families with a boy and a girl had a significantly higher mortality than children in families with two boys or two girls (odds ratio = 1.81, 95% confidence interval 1.17 to 2.82). The increase in risk was the same for boys and girls in families with two children one of whom was a boy and one a girl. CONCLUSION: Cross sexual transmission may be an important determinant of severity of measles infection.

Age Factors↗
PubMed1992

Analysis of the incubation period for measles in the epidemic in Greenland in 1951 using a variance components model.

This paper presents a model for analysing the incubation period of highly infectious diseases in populations where almost all susceptibles become infected during an epidemic. The model leads to a simple method for estimating the variance of the duration of the incubation period without any distributional assumptions. Further, the influence of covariates on the duration of the incubation period can be analysed. Data from the epidemic of measles in Greenland in 1951 are analysed and it is found that intersymptom times are correlated within households, suggesting that secondary cases are infected almost simultaneously. This result is inconsistent with a variation in the times of infection of secondary cases within a household which is often assumed when analysing data on measles. Prophylactic treatment did not prevent infection in the epidemic in Greenland, but it is found that the incubation period tended to be shorter for persons not receiving prophylactic treatment.

Analysis of Variance↗
PubMed1992

An epidemic in the field? Rapid assessment procedures and health research.

This paper reviews the development of various methods designed to generate relevant social information, pertaining to health and disease control, quickly and accurately. In so doing, we examine the use of KAP surveys and the subsequent development of community diagnosis, rapid appraisal methods, rapid epidemiological assessment, and rapid assessment procedures (RAP) for anthropological studies. Our focus is on the development of anthropological RAPs, in response to the lack of professionally trained social scientists to work with disease control programmes and ministries of health, and in light of the demonstrable need for social science input in the development of health policies and programmes. These developments are assessed in terms of scope and method. Issues relating to the representativeness, reliability and validity of RAP studies are discussed, and mechanisms by which to maximise the yield of valid data are presented.

Communicable Disease Control↗
PubMed1992

Patterns of exposure and severity of measles infection. Copenhagen 1915-1925.

Using data on children hospitalized with measles in Copenhagen from 1915 to 1925, I found that secondary cases (infected at home) exposed to two or more index cases had a higher case fatality rate than did children exposed to a single index case (relative risk (RR) = 1.90; 95% confidence interval (CI): 1.12 to 3.22). Compared with surviving cases, fatal secondary cases had a shorter interval between their own rashes and rash in the index case (P < .02), suggesting a shorter period of incubation for severe cases. Secondary cases infected by a severe case of measles had higher mortality (RR = 3.87; 95% CI: 1.65 to 9.08) than did secondary cases infected by an index case without pneumonia. These observations suggest that differences in patterns of exposure, possibly due to the dose of infection, may be important for understanding variation in measles mortality.

Child↗
PubMed1992

Severe measles outbreak in western Kenya.

During a measles outbreak investigation in Siaya district clustering of many measles cases were found to be an important determinant for measles mortality. A high proportion of cases were under one year of age. Case fatality rates were higher than previously reported from Kenya, particularly among infants. Vaccine efficacy was 18%. Alternative ways of protecting infants are discussed.

Child↗
PubMed1992

Lack of evidence of vertical transmission of human immunodeficiency virus type 2 in a sample of the general population in Bissau.

Twenty-nine human immunodeficiency virus type 2 (HIV-2) seropositive women identified in a cross-sectional study in Bissau in 1987 participated in a follow-up study in 1988, where each was matched for age and marital status with two HIV-2 seronegative women. Detailed information about all pregnancies was obtained. The HIV-2 seropositive women and their controls had similar mean numbers of pregnancies, live children, children who died, and abortions. The HIV-2 seropositive women did not have a greater risk of having had an abortion or a child who died than did the HIV-2 seronegative women. No difference in survival was seen between children born to HIV-2 seropositive and HIV-2 seronegative women. The H/S-ratios and CD4 numbers were lower in the seropositive group, but none had values lower than 0.4 and 0.4 x 10(9)/L, respectively. Seven prospectively observed children born to HIV-2 seropositive mothers showed no sign of infection. The lack of evidence of transmission of HIV-2 from mother to child is suggested to be due to the absence of marked immunodeficiency in this random sample of the general population.

Adult↗
PubMed1991

The role of sex in the transmission of measles in a Gambian village.

Data from the 1984-1985 epidemic of measles in Keneba, a Gambian village, have been reanalysed in order to test the effect of same sex vs. opposite sex transmission of measles on the severity of infection. A person infected by someone of the opposite sex was more likely to have severe infection with pulmonary complications than a person infected by someone of the same sex [RR (relative risk) = 2.8, 95% confidence interval (CI): 0.9-9.7]. A secondary case infected by someone of the opposite sex was significantly more likely to have a more severe illness relative to the primary case than a patient infected by someone of the same sex (P = 0.026, Fisher's exact test). There were slightly more female than male primary cases while male secondary cases had a higher risk than female cases of being infected by someone of the opposite sex (RR = 2.6, 95% CI: 0.9-6.9).

Disease Outbreaks↗
PubMed1991

Gender and the pattern of transmission of measles infection. A reanalysis of data from the Machakos area, Kenya.

Data on measles from the project in the Machakos district, Kenya between 1974 and 1981 have been reanalysed in order to test the impact of sex and cross-sex transmission on severity of infection. In families with several cases, the case fatality rate was high as 11.3% (13/115) during the initial 6 months of the project. In the remaining period, the case fatality rate fell to 2.4% (21/885) (relative risk (RR) = 0.21, 95% confidence interval (CI): 0.11-0.39). During the initial period with high mortality, second cases had 4.74 times higher mortality (95% CI: 1.65-13.66) than index cases and there was no difference in mortality between girls and boys (RR = 0.98). Among secondary cases, though not significant, those infected by someone of the opposite sex had a trend toward a higher risk of dying than those infected by someone of their own sex (RR = 2.44, 95% CI: 0.77-7.78). In families with two children of the same sex, the case fatality rate was 9% compared with 29% in families with a boy and a girl (RR = 3.49; 95% CI: 0.96-12.75). In the subsequent period with low mortality, the difference in mortality between index and secondary cases was less pronounced (RR = 2.32, 95% CI: 1.03-5.25) and girls had significantly higher case fatality than boys (RR = 2.63, 95% CI: 1.09-6.34). There was no difference in this case fatality rate associated with cross-sex transmission of infection (RR = 0.88).(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1991

Severity of measles and cross-sex transmission of infection in Copenhagen 1915-1925.

Using data on children hospitalized with measles in Copenhagen in 1915-1925, it was found that secondary cases infected at home by someone of the opposite sex had a relative case-fatality rate risk (RR) of 1.52 (95%, confidence interval (Cl): 0.80-2.88) compared with secondary cases infected by someone of the same sex. Males infected by a girl suffered more severely than when infected by another boy (RR = 2.46; 95% Cl: 1.00-6.04) whereas there was no difference for girls. In households with two cases of measles, case fatality was significantly higher in families with a boy and a girl infected at the same time compared with families with two boys or two girls (RR = 1.89; 95% Cl: 1.06-3.37). There was no difference in mortality in families with two boys or two girls having measles at the same time. These results strengthen previous observations from Guinea-Bissau that close contact with a child of the opposite sex increases the severity of measles infection.

Child↗
PubMed1990

Siblings of opposite sex as a risk factor for child mortality.

OBJECTIVE: To examine whether contracting an infection from a sibling of the opposite sex affects child mortality. DESIGN: Retrospective study of twins and case-control study of randomly selected children conducted within a prospective cohort study. SETTING: Urban and rural areas of Guinea-Bissau. SUBJECTS: 251 Pairs of twins (65 male pairs, 72 female pairs, and 114 mixed pairs), and 39 children who died and 78 controls identified in a cohort of 853 children aged less than 4, comprising 772 randomly selected children, all twins, and all children who had measles living in Bandim 2. MAIN OUTCOME MEASURES: Death of a child and sex of cotwin or older sibling nearest in age. RESULTS: The mortality among children from mixed pairs of twins was higher than that among pairs of the same sex (relative risk 1.47, 95% confidence interval 1.14 to 1.90). Boys had a slightly higher mortality especially in the older groups. In the case-control study the older sibling nearest in age was of the opposite sex for 29 (74%) of the children compared with 36 (46%) of the controls matched for age, sex, and area. Mortality was higher among both boys and girls with older siblings of the opposite sex than among those with siblings of the same sex (odds ratio 1.90, 0.78 to 4.61 v 7.5, 1.59 to 35.30), but the difference was more pronounced among girls. CONCLUSIONS: Children whose older sibling nearest in age is of the opposite sex or who have cotwins of the opposite sex have a higher mortality from infectious diseases. Further investigation is needed to determine the nature of this relation.

Adolescent↗
PubMed1990

Labelling of T cell subsets under field conditions in tropical countries. Adaptation of the immuno-alkaline phosphatase staining method for blood smears.

Immuno-alkaline phosphatase (AP) staining for T cell subsets (CD4 and CD8) of smears from fingerprick blood functioned well under tropical climatic conditions when smears were stored frozen with silica gel before being labelled. Unlabelled smears were stored for up to 12 months and could be transferred abroad without antigenic damage. Identical total CD4 and CD8 counts were obtained on venous and capillary blood, when compared using a FACS analyser. Although the AP method gave somewhat higher total CD4 and CD8 counts, the ratio remained the same. The major advantages of the method are: (i) no expensive equipment is required, (ii) only minute amounts of blood are needed, and (iii) slides can be stored for long periods before labelling and can be preserved for later reading. The method is suitable for community studies where there is a need for assessing the immune status of the population.

Alkaline Phosphatase↗
PubMed1990

Patterns of transmission and severity of measles infection: a reanalysis of data from the Machakos area, Kenya.

Data on measles from the project in the Machakos District, Kenya, 1974-1981, were reanalyzed. In families with several cases, secondary cases (children infected in the home) had a relative mortality risk of 3.00 (95% confidence interval [CI]: 1.55-5.80) compared with index cases who caught infection from someone outside the home. The case fatality rate (CFR) may be higher among secondary cases exposed to two or more index cases than among those exposed to only one index case (relative risk [RR] = 2.47; 95% CI: 0.93-6.56). The CFR was also higher among secondary cases exposed to a fatal index case than among those exposed to an index case who survived (RR = 4.69; 95% CI: 1.64-13.41). Children aged 12-23 months and those greater than or equal to 5 years were more likely than other age groups to have been infected by someone outside the home. During the course of the project the CFR in families with several cases was reduced from 8.8% to 2.7%. Though there is no general explanation for this tendency, it was observed that the proportion of secondary cases per index case was reduced during the last part of the project (odds ratio = 0.73; 95% CI: 0.56-0.95).

Age Factors↗
PubMed1990

Pattern of exposure and measles mortality in Senegal.

In a rural area of Senegal, 1500 cases of measles and 98 deaths (6.5%) were registered during a 4-year period (1983-1986). For children less than 5 years old, the acute case fatality ratio (CFR) was 9.6%. Compared with index cases who contracted measles in the village, secondary cases infected within the compound had a significantly higher mortality (odds ratio [OR], 2.9; 95% confidence interval [CI], 1.3-6.1). The CFR of secondary cases increased with the closeness of contact with the index cases; the ORs were 1.9 (CI, 0.6-6.0) for children living in the same compound but not the same household, 2.3 (CI, 1.0-5.7) for children living in the same household but not in the same hut, and 3.8 (CI, 1.7-8.4) for children living in the same hut. In large compounds with many cases, the CFR increased exponentially through the succession of generations; the ORs were 2.3 (CI, 1.0-5.2) in the second generation, 3.7 (CI, 1.1-3.0) in the third generation, 5.5 (CI, 1.7-18.1) in the fourth generation, and 16.1 (CI, 5.6-46.3) in the fifth or later generations. Postmeasles mortality through the year following measles infection was also significantly related to the intensity of exposure. Differences in exposure may be a major determinant of child survival, both at time of acute disease and for the long term impact of measles infection.

Acute Disease↗
PubMed1990

Measles incidence, vaccine efficacy, and mortality in two urban African areas with high vaccination coverage.

Measles incidence, vaccine efficacy, and mortality were examined prospectively in two districts in Bissau where vaccine coverage for children aged 12-23 months was 81% (Bandim 1) and 61% (Bandim 2). There was little difference in cumulative measles incidence before 9 months of age (6.1% and 7.6%, respectively). Between 9 months and 2 years of age, however, 6.1% contracted measles in Bandim 1 and 13.7% in Bandim 2. Even adjusting for vaccination status, incidence was significantly higher in Bandim 2 (relative risk 1.6, P = .04). Even though 95% of the children had measles antibodies after vaccination, vaccine efficacy was not more than 68% (95% confidence interval [CI] 39%-84%) and was unrelated to age at vaccination. Unvaccinated children had a mortality hazard ratio of 3.0 compared with vaccinated children (P = .002), indicating a protective efficacy against death of 66% (CI 32%-83%) of measles vaccination. These data suggest that it will be necessary to vaccinate before age 9 months to control measles in hyperendemic urban African areas.

Age Factors↗
PubMed1990

Delayed excess mortality after exposure to measles during the first six months of life.

In an urban area of Guinea-Bissau, 71 children exposed to measles before age 6 months had a mortality risk of 34% (95% confidence interval (Cl) 24-47) between 6 and 60 months of age. The mortality risk for the 205 other children of the same birth cohort who had not been exposed to or developed measles was 11% (95% Cl 9-15), a significant difference compared with exposed children. With a version of the Cox regression model, maternal education was found to be the only background factor with a significant effect on mortality. When background factors were controlled for, the mortality of children exposed to measles was significantly higher than that of controls in each of the age intervals 6-11, 12-23, and 24-35 months. For the large subgroup of children of mothers without any formal education, exposed children had 5.7 times (95% Cl 2.7-12.0) higher mortality than did the control children in the age interval 6-35 months. Diarrhea deaths were particularly common among exposed children. Of 22 children who had been exposed before age 6 months during a subsequent epidemic and had a blood test taken, there was a significantly higher mortality risk (27%) between 6 months and 5 years than in the 26 controls who had a blood test (0%). Children who had elevated antibody titers to measles after exposure had a particularly high mortality compared with controls. These results suggest that later childhood mortality may be related to infectious experiences during the first months of life. The possible long-term health consequences of exposure to measles virus should be considered when assessing the value of measles control programs.

Child, Preschool↗