|It is commonly assumed that infections are harmful but with limited long-term consequences. It is rarely examined whether some infections might be good for at least some individuals. However, research in measles and measles immunisation at The Bandim Project in Guinea-Bissau has indicated that this possibility should be considered. If this is true — it could have a large impact on the immunisation and disease control strategies. The studies below were performed on this background.
The field studies were performed in Guinea-Bissau. The PhD thesis is based on four articles: Two papers are dealing with the determinants for the severity of acute chickenpox, and two papers with long-term consequences of viral infections. The two follow-up studies assessed the health of children who had chickenpox before the age of two years, and the health of children who had acute lower respiratory infection with respiratory syncytial virus (RSV).
Varicella-Zoster infection (Chickenpox) acute infection
In the first study, 165 cases of chickenpox were examined. The diagnosis was recognised correctly by Guinean mothers. The age distribution in Guinea-Bissau resembled the pattern in developed countries. Nutritional status did not influence severity of infection. Cases infected in the house in which they lived (secondary cases) had more pox (p<0.01), the difference being particularly pronounced for girls.
In the second study, a total of 1539 acute cases of chickenpox were included. Of these 551 cases were secondary cases. Secondary cases had more severe infection measured by number of pox than the index cases, and the number of pox was related to the intensity of exposure. During the acute chickenpox infection many children suffered from complications like pneumonia (ca. 10%), and a total of 40% of the children were treated with antibiotics either because of pneumonia or skin infection. The complications were related to the number of pox and to being a secondary case. Two deaths directly associated with acute infection were registered.
Varicelia zoster follow-up
According to the results of the 6-month follow-up, children who have had chickenpox, do not in general have a worse state of health than children who have not have had the disease. The weight was actually higher in the girls who had had chickenpox. However, previous chickenpox cases may continue to have an excess of skin infections for at least 6 months. Chickenpox had no negative effect on long-term child survival.
The RSV follow-up study
A total of 335 children with verified RSV in the first two years of life were examined at the age of 6-7 years. Each child had a matched control. Health status was related to the primary severity (measured by hospital contact) of the RSV infection, and to being antigen-positive. In former RSV-positive infants lung-function was decreased. Atopy was not increased measured by skin-prick test and IgE.
The risk factors for severity of chickenpox resemble those identified for other viral infections such as polio, pertussis, and measles, i.e. intensity of exposure. Considerable morbidity during the acute illness was observed. No negative long-term consequences of chickenpox were identified, and chickenpox may actually be positive for growth.
RSV ALRI in infancy had an impact on the morbidity and lung function at the age of school start. Severe illness (diagnosis at consultation in contrast to at home) was a risk factors for adverse long-term health consequences.
Different viral diseases may have common determinants for severe infection due to the role of intensive exposure in enhancing the dose of infection, shortening the period of incubation and aggravating clinical severity.