European Journal of Clinical Microbiology & Infectious Diseases

, Volume 30, Issue 3, pp 435–437

How frequent is varicella-associated pneumonia in children?

Authors

    • Pediatric DepartmentHospital Comarcal de Inca
  • V. Henales
    • Department of Pediatric RadiologyHospital Son Dureta
  • S. Yeste
    • Hospital de Manacor
  • J. Figuerola
    • Pediatric Department, Pediatric Pneumology SectionHospital Son Dureta
  • J. Hervás
    • Pediatric Department, Pediatric Infectious Disease SectionHospital Son Dureta
Article

DOI: 10.1007/s10096-010-1106-9

Cite this article as:
Hervás, D., Henales, V., Yeste, S. et al. Eur J Clin Microbiol Infect Dis (2011) 30: 435. doi:10.1007/s10096-010-1106-9

Abstract

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.

Introduction

Chickenpox is a very contagious disease caused by varicella-zoster virus that mostly affects children in the course of epidemics [1]. According to a seroepidemiologic study performed in Spain, 90.9% of the population under 14 years of age was already immune [2]. 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 [3]. 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.

Methods

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 [4]. Clinical records of the children hospitalized for varicella and pneumonia were reviewed. Chest X-rays were evaluated by a pediatric pneumologist and radiologist.

Pneumonia was classified into three groups, depending on the radiological, clinical, microbiological, and laboratory findings (Table 1) [58]. Bacterial pneumonia was defined as: (a) suggestive chest X-rays and one or more clinical, microbiological, or laboratory findings; (b) non-suggestive radiological pattern but clinical, laboratory, and microbiological findings all suggestive of bacterial pneumonia. Viral non-varicella pneumonia was defined as: (a) suggestive radiological findings and one or more clinical, microbiological, or laboratory findings; (b) non-suggestive radiological viral but clinical, laboratory, and microbiological findings all suggestive of viral pneumonia. Varicella pneumonitis was diagnosed when a typical radiological finding was observed within 7 days of the appearance of the varicella rash.
Table 1

Criteria used for defining the etiology of pneumonia

 

Chest X-rays

Laboratory

Microbiological

Clinical

Bacterial

Lobar alveolar infiltrates

Pleural fluid

CRP >12 mg/dl

Blood culture

Pleural effusion culture

Direct pneumonic focus culture

Fever >39°C

Viral

Bilateral interstitial infiltrates

CRP <2 mg/dl

Culture or antigen detection in nasopharyngeal aspirates

Antibody seroconversion

Fever <39°C

Varicella

Reticular/nodular infiltrates

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.

Results

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.

After clinical, radiological, laboratory, and microbiological studies, 9/17 (53%) patients were considered to have bacterial pneumonia, 7/17 (41%) viral pneumonia, and 1/17(6%) varicella pneumonitis (typical micronodular affectation of lung X-rays). All patients were immunocompetent and were not receiving any chronic treatment. A microbiological diagnosis was obtained in 2/9 bacterial pneumonia cases (Streptococcus pyogenes in two blood cultures). The child who developed varicella pneumonitis was a 12-month-old infant who was admitted after 4 days of fever and varicella rash. During his hospitalization, S. aureus was isolated in the bloodstream. Viral isolation was obtained in 3/7 suspected viral pneumonia cases (two cases of respiratory syncytial virus and one case of adenovirus). Statistical differences (p < 0.05) in the median of the age and the time from fever and varicella rash to hospitalization were observed between suspected bacterial and viral pneumonia cases. The main clinical and outcome characteristics for each suspected etiology are summarized in Table 2.
Table 2

Clinical characteristics and outcome of the patients hospitalized with pneumonia and varicella infection

Diagnosis

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 (%)

Bacterial pneumonia

2.6 (1.3–4.4)

5.9 (0–8)

4.1 (0–12)

89%

15 (4–101)

3/9 (33%)

4/9 (44%)

Viral pneumonia

1.2 (0.2–3.1)

2.4 (0–5)

2.2 (0–5)

78%

9.5 (2–18)

2/7 (29%)

2/7 (29%)

Varicella pneumonia

1.4

4

4

100%

13

1/1

0

Discussion

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 [1114], with varicella pneumonitis being the most important cause of morbidity and mortality in adult varicella [3]. This complication is associated with 30% of deaths for varicella complications in this age group [10]. 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 [3]. This observation differs from that of Galil et al. [3] 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.

Copyright information

© Springer-Verlag 2010