How frequent is varicella-associated pneumonia in children?
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- Hervás, D., Henales, V., Yeste, S. et al. Eur J Clin Microbiol Infect Dis (2011) 30: 435. doi:10.1007/s10096-010-1106-9
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Varicella is a frequent though mild infection in children, but it can cause important morbidity in adults. The most frequent complication in adults is varicella pneumonia. However, lower airway complications associated to varicella have been scarcely studied in children. We retrospectively reviewed the clinical records of the children hospitalized for varicella-associated pneumonia in the three public hospitals on the Island of Mallorca. We discovered that 17/213 (8%) children hospitalized for varicella were diagnosed of pneumonia. The rate of hospitalization for varicella complication due to pneumonia was 4.3 cases per 10,000 varicella infections. Only one patient was diagnosed of varicella pneumonia, which accounts for 0.3 cases per 10,000 varicella infections. Nine of 17 (53%) cases were classified as bacterial pneumonia. Statistical differences (p < 0.05) in the median time from rash (5.9 vs. 2.4 days) and fever (4.1 vs. 2.2 days) to admission were observed between bacterial and viral pneumonia. However, outcome differences measured by the median length of stay, need for oxygen, and admission to the intensive care unit were not observed. Varicella pneumonia is a very rare complication of varicella in children. Most of the lower airway infections in the course of varicella are associated to other co-infections.
Chickenpox is a very contagious disease caused by varicella-zoster virus that mostly affects children in the course of epidemics . According to a seroepidemiologic study performed in Spain, 90.9% of the population under 14 years of age was already immune . Varicella is usually a benign disease in children, but the rate of complications increase in adulthood. Varicella pneumonitis is the most important complication in adults, occurring in 3.4 to 4.3 cases per 10,000 adults with chickenpox . In spite of the high morbidity of varicella pneumonia in adults, cases in children are very scarce in the literature. In this study, we analyze the incidence and characteristics of pneumonia associated to varicella infection on the island of Mallorca, Spain.
We studied the incidence and characteristics of pneumonia associated to varicella infection in Mallorca, Spain, during the years 1995 to 2005. The number of cases of varicella infection and hospitalizations for varicella complications in this period were obtained as previously described . Clinical records of the children hospitalized for varicella and pneumonia were reviewed. Chest X-rays were evaluated by a pediatric pneumologist and radiologist.
Criteria used for defining the etiology of pneumonia
Lobar alveolar infiltrates
CRP >12 mg/dl
Pleural effusion culture
Direct pneumonic focus culture
Bilateral interstitial infiltrates
CRP <2 mg/dl
Culture or antigen detection in nasopharyngeal aspirates
Statistical analysis was performed using the BioStat 5.1.3 software package (AnalystSoft). The data distribution was given as the median and range. Differences between groups were studied with the Mann–Whitney U-test. Statistical significance was set as p < 0.05.
A total of 213 children were admitted to the three public hospitals of the island with a diagnosis of varicella. Seventeen of 213 (8%) children were diagnosed with pneumonia. The rate of hospitalization for varicella complication due to pneumonia was 4.3 cases per 10,000 varicella infections and 0.3 varicella pneumonitis cases per 10,000 varicella infections. The median age was 1.9 years (range 0–4 years), the median length of hospital stay was 11 days (range 2–101 days), and 10/17 (59%) were male.
The median time from fever and varicella rash to hospitalization was 3.1 and 4.5 days, respectively. Six of 17 (35%) were admitted in the pediatric intensive care unit (one for clinical sepsis, three for empyema, one for severe laryngitis, and one for hypoxia). Four patients presented with pleural effusion. Acyclovir was prescribed in 9/17 (53%) children hospitalized for varicella complicated with pneumonia. Regardless of the etiological diagnosis, all patients received treatment with antibiotics.
Clinical characteristics and outcome of the patients hospitalized with pneumonia and varicella infection
Median age (years)
Median time from rash to admission (days)
Median time from fever to admission (days)
% of patients with temperature >39°C
Median length of hospital stay (days)
Oxygen requirement (%)
Admission to intensive care unit (%)
In this study, we have analyzed varicella-associated pneumonia, the most frequent complication of primary varicella infection. In children, previous studies have reported rates of pneumonia ranging from 7 to 25% of children hospitalized for varicella complications [9, 10]. In our study, varicella was the third most frequent cause of hospitalization for varicella (8%). Despite it being an important cause of complications in the course of varicella infection, few studies deal with varicella-associated pneumonia in children. Most cases of varicella-associated pneumonia are reported in adult patients [11–14], with varicella pneumonitis being the most important cause of morbidity and mortality in adult varicella . This complication is associated with 30% of deaths for varicella complications in this age group . However, it seems to be infrequent in children as suggested by the lack of reports. In our population study, we have found only 0.3 cases of varicella pneumonitis per 10,000 varicella infections . This observation differs from that of Galil et al.  in adults, where the rate of lower respiratory infection was 3.9 cases per 10,000 varicella cases. Also different from adults, we have observed that most of the pulmonary complications of varicella in children seem to be produced by co-infections and not directly by varicella infection.
Our study has several limitations. First, it is a retrospective study with its drawbacks and bias. Second, we obtained the prevalence of varicella pneumonia using the total children population and the estimated rate of varicella infection in our children population based on varicella notifications from the primary care sentinel centers. Lastly, the lack of standards to differentiate viral from bacterial pneumonia makes it difficult to validate the accuracy of our classification.