Severe influenza cases in paediatric intensive care units in Germany during the pre-pandemic seasons 2005 to 2008

Severe influenza virus infection in children admitted to the PICU: Comparison of influenza A and influenza B virus infection

Although the influenza virus usually causes a self-limiting disease, deaths are reported even in children without risk factors. We aimed to identify the clinical features, mortality associated with severe influenza A and B virus infections of children admitted to the pediatric intensive care unit (PICU). We conducted a retrospective study of children with confirmed influenza infection between 2012 and 2019 who were admitted to the PICU. Demographic features, risk factors, clinical data, microbiological data, complications, and outcomes were collected. Over seven influenza seasons (2012-2011 to 2015-2016), 713 children diagnosed with laboratory-confirmed influenza-related LRTI, and PICU admission was needed in 6% (46/713) of the patients. Thirty-one patients (67.4%) were diagnosed with influenza A and 15 patients were diagnosed with influenza B. Epidemiologic and clinical characteristics were similar in both influenza types, lactate dehydrogenase levels were significantly higher for influenza A than for influenza B infections. Although the influenza A to B ratio among the patients admitted to the PICU was 2.06, the percentage of cases requiring PICU admission was nearly two times higher in influenza B cases. There was no statistically significant difference in disease severity and complications in patients with influenza A and influenza B.

Detection of influenza epidemics using hidden Markov and Serfling approaches

OBJECTIVE

Detection of epidemics is a critical issue in epidemiology of infectious diseases which enable healthcare system to better control it. This study is devoted to investigating the 5-year trend in influenza and severe acute respiratory infection cases in Iran. The epidemics were also detected using the hidden Markov model (HMM) and Serfling model.

STUDY DESIGN

In this study, we used SARI data reported in the World Health Organization (WHO) FluNet web-based tool from August 2011 to August 2016.

METHODS

SARI data in Iran from August 2011 to August 2016 were used. We applied the HMM and Serfling model for indicating the two epidemic and non-epidemic phases. The registered outbreak activity recorded on the WHO website was used as the gold standard. The coefficient of determination was reported to compare the goodness of fit of the models.

RESULTS

Serfling models modified by 30% and 35% of the data had a sensitivity of 91.67% and 95.83%, while for 15%, 20% and 25% were 70.83%, 79.17% and 83.33%, respectively. Sensitivity of HMM and autoregressive HMM (AHMM) was 66.67% and 92.86%. All fitted models have a specificity of over 96%. The R² for HMM and AHMM was calculated 0.73 and 0.85, respectively, showing better fitness of these models, while R² was around 50% for different types of Serfling models.

CONCLUSIONS

Both modified Serfling and HMM were acceptable models in determining the epidemic points for the detection of weekly SARI. The AHMM had better fitness, higher detection power and more accurate detection of the incidence of epidemics than Serfling model and high sensitivity and specificity. In addition to AHMM, Serfling models with 30% and 35% modification can be used to detect epidemics due to approximately the same accuracy but the simplicity of the calculations.

Adenoviral Respiratory Infection-Associated Mortality in Children: A Retrospective Case Series

Viral respiratory infections are a leading cause of illness and hospitalization in young children worldwide. Case fatality rates in pediatric patients with adenoviral lower respiratory tract infection requiring intensive care unit (ICU) admission have been reported between 7 and 22%. We investigated the demographics and clinical characteristics in pediatric mortalities associated with adenoviral respiratory infection at 12 academic children's hospitals in the United States. There were 107 mortality cases included in our study, 73% of which had a chronic medical condition. The most common chronic medical condition was immunocompromised state in 37 cases (35%). The incidences of pediatric acute respiratory distress syndrome (78%) and multiple organ dysfunction syndrome (94%) were profound. Immunocompetent cases were more likely to receive mechanical ventilation within the first hour of ICU admission (60 vs. 14%, p < 0.001) and extracorporeal membrane oxygenation (27 vs. 5%, p = 0.009), and less likely to receive continuous renal replacement therapy (20 vs. 49%, p = 0.002) or have renal dysfunction (54 vs. 78%, p = 0.014) as compared with immunocompromised cases. Immunocompromised cases were more likely to have bacteremia (57 vs. 16%, p < 0.001) and adenoviremia (51 vs. 17%, p < 0.001) and be treated with antiviral medications (81 vs. 26%, p < 0.001). We observed a high burden of nonrespiratory organ system dysfunction in a cohort of pediatric case fatalities with adenoviral respiratory infection. The majority of cases had a chronic medical condition associated with an increased risk of complications from viral respiratory illness, most notably immunocompromised state. Important treatment differences were noted between immunocompromised and immunocompetent cases.

Prospective surveillance of antiviral resistance in hospitalized infants less than 12 months of age with A(H3N2) influenza infection and treated with oseltamivir

BACKGROUND

Infants exhibit elevated influenza virus loads and prolonged viral shedding, which may increase the risk for resistance development, especially in cases of suboptimal exposure to antiviral therapy.

METHODS

We performed a prospective surveillance of hospitalized infants undergoing oseltamivir therapy during the 2008-2009 and 2011-2012 influenza seasons at two paediatric hospitals in Germany. A total of 37 infants less than 1 year of age with laboratory confirmed influenza A(H3N2) infection received oseltamivir as per physician's order for 5 days (2008-2009 season: 2 mg/kg twice daily; 2011-2012 season: 2.0 mg/kg; 2.5 mg/kg and 3.0 mg/kg twice daily for infants <1 month; 2-3 months and 4-12 months, respectively). Virus load, the susceptibility to neuraminidase inhibitors (NAIs), and the presence of molecular markers of resistance to NAIs was assessed for influenza viruses recovered from respiratory samples collected at baseline and during follow-up visits.

RESULTS

Overall, 73% of the infants continued to shed viral RNA detectable by reverse transcription (RT)-PCR after dose number 10 of oseltamivir; 12 infants shed viruses, 2 of them (both 9 months of age) shed resistant viruses. Resistance was characterized by ≥1,000-fold increase of 50% inhibitory concentration (IC₅₀) for oseltamivir, up to 50-fold for zanamivir and elevated Km values when compared to susceptible A(H3N2) strains. Sanger sequencing revealed the selection of the NA-R292K substitution in both instances (after dose number 10 on day 6).

CONCLUSIONS

Our data suggest that it may be relevant to monitor antiviral resistance systematically in all infants, considering that the European Medicines Agency has recently extended the licensure for oseltamivir to include full-term infants.

Epidemiology of Australian Influenza-Related Paediatric Intensive Care Unit Admissions, 1997-2013

BACKGROUND

Influenza virus predictably causes an annual epidemic resulting in a considerable burden of illness in Australia. Children are disproportionately affected and can experience severe illness and complications, which occasionally result in death.

METHODS

We conducted a retrospective descriptive study using data collated in the Australian and New Zealand Paediatric Intensive Care (ANZPIC) Registry of influenza-related intensive care unit (ICU) admissions over a 17-year period (1997-2013, inclusive) in children <16 years old. National laboratory-confirmed influenza notifications were used for comparison.

RESULTS

Between 1997 and 2013, a total of 704 influenza-related ICU admissions were recorded, at a rate of 6.2 per 1,000 all-cause ICU admissions. Age at admission ranged from 0 days and 15.9 years (median = 2.1 years), with 135 (19.2%) aged <6 months. Pneumonia/pneumonitis and bronchiolitis were the most common primary diagnoses among influenza-related admissions (21.9% and 13.6%, respectively). More than half of total cases (59.2%) were previously healthy (no co-morbidities recorded), and in the remainder, chronic lung disease (16.7%) and asthma (12.5%) were the most common co-morbidities recorded. Pathogen co-detection occurred in 24.7% of cases, most commonly with respiratory syncytial virus or a staphylococcal species. Median length of all ICU admissions was 3.2 days (range 2.0 hours- 107.4 days) and 361 (51.3%) admissions required invasive respiratory support for a median duration of 4.3 days (range 0.2 hours- 107.5 days). There were 27 deaths recorded, 14 (51.9%) in children without a recorded co-morbidity.

CONCLUSION

Influenza causes a substantial number of ICU admissions in Australian children each year with the majority occurring in previously healthy children.

An inception cohort study assessing the role of pneumococcal and other bacterial pathogens in children with influenza and ILI and a clinical decision model for stringent antibiotic use

BACKGROUND

Influenza-like illness (ILI) is a common reason for paediatric consultations. Viral causes predominate, but antibiotics are used frequently. With regard to influenza, pneumococcal coinfections are considered major contributors to morbidity/mortality.

METHODS

In the context of a perennial quality management (QM) programme at the Charité Departments of Paediatrics and Microbiology in collaboration with the Robert Koch Institute, children aged 0-18 years presenting with signs and symptoms of ILI were followed from the time of initial presentation until hospital discharge (Charité Influenza-Like Disease = ChILD Cohort). An independent QM team performed highly standardized clinical assessments using a disease severity score based on World Health Organization criteria for uncomplicated and complicated/progressive disease. Nasopharyngeal and pharyngeal samples were collected for viral reverse transcription polymerase chain reaction and bacterial culture/sensitivity and MaldiTOF analyses. The term 'detection' was used to denote any evidence of viral or bacterial pathogens in the (naso)pharyngeal cavity. With the ChILD Cohort data collected, a standard operating procedure (SOP) was created as a model system to reduce the inappropriate use of antibiotics in children with ILI. Monte Carlo simulations were performed to assess cost-effectiveness.

RESULTS

Among 2,569 ChILD Cohort patients enrolled from 12/2010 to 04/2013 (55% male, mean age 3.2 years, range 0-18, 19% >5 years), 411 patients showed laboratory-confirmed influenza, with bacterial co-detection in 35%. Influenza and pneumococcus were detected simultaneously in 12/2,569 patients, with disease severity clearly below average. Pneumococcal vaccination rates were close to 90%. Nonetheless, every fifth patient was already on antibiotics upon presentation; new antibiotic prescriptions were issued in an additional 20%. Simulation of the model SOP in the same dataset revealed that the proposed decision model could have reduced the inappropriate use of antibiotics significantly (P<0.01) with an incremental cost-effectiveness ratio of -99.55€.

CONCLUSIONS

Physicians should be made aware that in times of pneumococcal vaccination the prevalence and severity of influenza infections complicated by pneumococci may decline. Microbiological testing in combination with standardized disease severity assessments and review of vaccination records could be cost-effective, as well as promoting stringent use of antibiotics and a personalized approach to managing children with ILI.

Continued high incidence of children with severe influenza A(H1N1)pdm09 admitted to paediatric intensive care units in Germany during the first three post-pandemic influenza seasons, 2010/11-2012/13

BACKGROUND

Previous influenza surveillance at paediatric intensive care units (PICUs) in Germany indicated increased incidence of PICU admissions for the pandemic influenza subtype A(H1N1)pdm09. We investigated incidence and clinical characteristics of influenza in children admitted to PICUs during the first three post-pandemic influenza seasons, using active screening.

METHODS

We conducted a prospective surveillance study in 24 PICUs in Bavaria (Germany) from October 2010 to September 2013. Influenza cases among children between 1 month and 16 years of age admitted to these PICUs with acute respiratory infection were confirmed by PCR analysis of respiratory secretions.

RESULTS

A total of 24/7/20 influenza-associated PICU admissions were recorded in the post-pandemic seasons 1/2/3; incidence estimates per 100,000 children were 1.72/0.76/1.80, respectively. Of all 51 patients, 80% had influenza A, including 65% with A(H1N1)pdm09. Influenza A(H1N1)pdm09 was almost absent in season 2 (incidence 0.11), but dominated PICU admissions in seasons 1 (incidence 1.35) and 3 (incidence 1.17). Clinical data was available for 47 influenza patients; median age was 4.8 years (IQR 1.6-11.0). The most frequent diagnoses were influenza-associated pneumonia (62%), bronchitis/bronchiolitis (32%), secondary bacterial pneumonia (26 %), and ARDS (21%). Thirty-six patients (77 %) had underlying medical conditions. Median duration of PICU stay was 3 days (IQR 1-11). Forty-seven per cent of patients received mechanical ventilation, and one patient (2%) extracorporeal membrane oxygenation; 19% were treated with oseltamivir. Five children (11%) had pulmonary sequelae. Five children (11%) died; all had underlying chronic conditions and were infected with A(H1N1)pdm09. In season 3, patients with A(H1N1)pdm09 were younger than in season 1 (p = 0.020), were diagnosed more often with bronchitis/bronchiolitis (p = 0.004), and were admitted to a PICU later after the onset of influenza symptoms (p = 0.041).

CONCLUSIONS

Active screening showed a continued high incidence of A(H1N1)pdm09-associated PICU admissions in the post-pandemic seasons 1 and 3, and indicated possible underestimation of incidence in previous German studies. The age shift of severe A(H1N1)pdm09 towards younger children may be explained by increasing immunity in the older paediatric population. The high proportion of patients with underlying chronic conditions indicates the importance of consistent implementation of the current influenza vaccination recommendations for risk groups in Germany.

The outcomes of children with pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVE

To provide additional details and evidence behind the recommendations for outcomes assessment of patients with pediatric acute respiratory distress syndrome from the Pediatric Acute Lung Injury Consensus Conference.

DESIGN

Consensus conference of experts in pediatric acute lung injury.

METHODS

A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The outcomes subgroup comprised four experts. When published data were lacking, a modified Delphi approach emphasizing strong professional agreement was used.

RESULTS

The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, seven of which related to outcomes after pediatric acute respiratory distress syndrome. All seven recommendations had strong agreement. Children with acute respiratory distress syndrome continue to have a high mortality, specifically, in relation to certain comorbidities and etiologies related to pediatric acute respiratory distress syndrome. Comorbid conditions, such as an immunocompromised state, increase the risk of mortality even further. Likewise, certain etiologies, such as non-pulmonary sepsis, also place children at a higher risk of mortality. Significant long-term effects were reported in adult survivors of acute respiratory distress syndrome: diminished lung function and exercise tolerance, reduced quality of life, and diminished neurocognitive function. Little knowledge of long-term outcomes exists in children who survive pediatric acute respiratory distress syndrome. Characterization of the longer term consequences of pediatric acute respiratory distress syndrome in children is vital to help identify opportunities for improved therapeutic and rehabilitative strategies that will lessen the long-term burden of pediatric acute respiratory distress syndrome and improve the quality of life in children.

CONCLUSIONS

The Consensus Conference developed pediatric-specific recommendations for pediatric acute respiratory distress syndrome regarding outcome measures and future research priorities. These recommendations are intended to promote optimization and consistency of care for children with pediatric acute respiratory distress syndrome and identify areas of uncertainty requiring further investigation.

Airway mucosal immune-suppression in neonates of mothers receiving A(H1N1)pnd09 vaccination during pregnancy

BACKGROUND

It is recommended to vaccinate pregnant women against influenza. A possible impact on the immune expression of the fetus has never been studied. We aim to study the immune signature in the upper airways and the incidence of infections in neonates born to mothers receiving Influenza A(H1N1)pnd09 vaccination during pregnancy.

METHODS

One hundred and fifty-six women from the unselected Copenhagen Prospective Study on Asthma in Childhood (COPSAC2010) received Influenza A(H1N1)pnd09-vaccination during the 2009 pandemic. Fifty-one mothers received the vaccine during pregnancy and 105 after pregnancy; 332 neonates of nonvaccinated mothers were included as secondary controls. Nasal mucosal lining fluid was sampled in 488 neonates and assessed for interleukin (IL)-12p70, IP-10, interferon-gamma (IFN)-γ, tumor necrosis factor-alpha (TNF)-α, MIP-1β, MCP-1, MCP-4, IL-4, IL-5, IL-13, eotaxin-1, eotaxin-3, TARC, MDC, IL-17, IL-1β, IL-8, transforming growth factor beta (TGF)-β1, IL-10 and IL-2. Infections were monitored the first year of life by daily diary cards and clinical controls.

RESULTS

Neonates of mothers vaccinated during pregnancy had significant up-regulation of TGF-β1 [ratio = 1.52 (1.22-1.90), P = 0.0002], and corresponding down-regulation (P < 0.05) of IL-12p70, IFN-γ, IL-5, eotaxin-1, TARC, MDC, IL-8 in comparison to those vaccinated after pregnancy. The lag-time from vaccination during pregnancy to assessment of the immune signature showed significant and positive association to up-regulation of TGF-β1 levels (P = 0.0003) and significant negative association to other mediators. The study was not powered to study differences in the incidence of infections in early infancy which did not differ between the study groups.

CONCLUSION

Influenza A(H1N1)pnd09 vaccination during pregnancy up-regulates TGF-β1 and down-regulates key mediators of the protective immunity.

Prevalence of antibodies against influenza A and B viruses in children in Germany, 2008 to 2010

The prevalence of influenza A and B virus-specific IgG was determined in sera taken between 2008 and 2010 from 1,665 children aged 0-17 years and 400 blood donors in Germany. ELISA on the basis of whole virus antigens was applied. Nearly all children aged nine years and older had antibodies against influenza A. In contrast, 40% of children aged 0-4 years did not have any influenza A virus-specific IgG antibodies. Eightysix percent of 0-6 year-olds, 47% of 7-12 year-olds and 20% of 13-17 year-olds were serologically naïve to influenza B viruses. By the age of 18 years, influenza B seroprevalence reached approximately 90%. There were obvious regional differences in the seroprevalence of influenza B in Germany. In conclusion, seroprevalences of influenza A and influenza B increase gradually during childhood. The majority of children older than eight years have basal immunity to influenza A, while comparable immunity against influenza B is only acquired at the age of 18 years. Children aged 0-6 years, showing an overall seroprevalence of 67% for influenza A and of 14% for influenza B, are especially at risk for primary infections during influenza B seasons.

The burden of seasonal and pandemic influenza in infants and children

The burden of influenza is unevenly distributed, with more severe outcomes in children aged <5 years than older children and adults. In spite of this, immunisation policies for young children are far from universal. This article provides an overview of the published evidence on the burden of influenza in children worldwide, with a particular interest in the impact of pandemic influenza in 2009-2010 (caused by the H1N1pdm09 virus). In an average season, up to 9.8 % of 0- to 14-year olds present with influenza, but incidence rates can be markedly higher in younger children. Children aged <5 years have greater rates of hospitalisation and complications than their older counterparts, particularly if the children have co-existing illnesses; historically, this age group have had higher mortality rates from the disease than other children, although during the 2009-2010 pandemic the median age of those who died of influenza was higher than in previous seasons. Admissions to hospital and emergency departments appear to have been more frequent in children with H1N1pdm09 infections than during previous seasonal epidemics, with pneumonia continuing to be a common complication in this setting. Outcomes in children hospitalised with severe disease also seem to have been worse for those infected with H1N1pdm09 viruses compared with seasonal viruses. Studies in children confirm that vaccination reduces the incidence of seasonal influenza and the associated burden, underlining the importance of targeting this group in national immunisation policies.

CONCLUSIONS

Children aged <5 years are especially vulnerable to influenza, particularly that caused by seasonal viruses, and vaccination in this group can be an effective strategy for reducing disease burden.

Unchanged severity of influenza A(H1N1)pdm09 infection in children during first postpandemic season

Improvement is needed in preventing severe disease and nosocomial transmission in children beyond pandemic situations.

We conducted a nationwide hospital-based prospective study in Germany of influenza A(H1N1)pdm09 cases among children <15 years of age admitted to pediatric intensive care units and related deaths during the 2009–10 pandemic and the 2010–11 postpandemic influenza seasons. We identified 156 eligible patients: 112 in 2009–10 and 44 in 2010–11. Although a shift to younger patients occurred in 2010–11 (median age 3.2 vs. 5.3 years), infants <1 year of age remained the most affected. Underlying immunosuppression was a risk factor for hospital-acquired infections (p = 0.013), which accounted for 14% of cases. Myocarditis was predictive of death (p = 0.006). Of the 156 case-patients, 17% died; the difference between seasons was not significant (p = 0.473). Our findings stress the challenge of preventing severe postpandemic influenza infection in children and the need to prevent nosocomial transmission of influenza virus, especially in immunosuppressed children.

The coming era of quadrivalent human influenza vaccines: who will benefit?

Influenza vaccines form the mainstay of public health and personal protection against infection with seasonal influenza viruses. These vaccines are designed to protect people against infection with the currently circulating influenza viruses. Since the late 1970s, this has required the use of a trivalent vaccine consisting of two influenza A viruses and one influenza B virus. However, since the early 2000s, a second lineage of B viruses has regularly circulated in many countries that is quite distinct, with only low levels of cross protection between the two lineages. Due to the difficulties in determining which B lineage will circulate, and matching this with the vaccine to be administered some 6-9 months later, there has been an increasing interest in the development of quadrivalent influenza vaccines, containing two influenza B viruses representing both lineages. Development has been rapid and we are now on the cusp of a new generation of influenza vaccines becoming available. This paper discusses the issues and rationale behind this welcome development and who is likely to benefit most.

Pulmonary bacterial coinfection in infants and children with viral respiratory infection

The true incidence of pulmonary bacterial coinfection in infants and children hospitalized with a viral respiratory infection is difficult to ascertain but can vary widely from under 1 to 44%. For the same patient group admitted to pediatric intensive care units and/or requiring ventilatory support, the evidence is more convincing, with reported incidences of 17-39%. Studies covering influenza and respiratory syncytial virus infection dominate the recent literature. Whether treatment (or 'cover') with antibiotics is indicated/justified lies in the balance of risk of pulmonary bacterial coinfection (or risk of not diagnosing it), severity of disease and the patient setting. The balance between the overprescription of antibiotics and the possible sequelae associated with bacterial coinfection in infants and children continues to fuel debate.

The clinical characteristics and direct medical cost of influenza in hospitalized children: a five-year retrospective study in Suzhou, China

Background

There have been few studies on children hospitalized with influenza published from mainland China. We performed a retrospective review of medical charts to describe the epidemiology, clinical features and direct medical cost of laboratory-proven influenza hospitalized children in Suzhou, China.

Methods

Retrospective study on children with documented influenza infection hospitalized at Suzhou Children Hospital during 2005–2009 was conducted using a structured chart review instrument.

Results

A total of 480 children were positive by immuno-fluorescent assay for influenza during 2005–2009. The hospitalizations for influenza occurred in 8–12 months of the year, most commonly in the winter with a second late summer peak (August-September). Influenza A accounted for 86.3%, and of these 286 (59.6%) were male, and 87.2% were <5 years of age. The median length of hospital stay was 7 days. Fever was the most common symptom, occurring in 398 (82.9%) children. There were 394 (82.1%) children with pneumonia and 70.2% of these hospitalized children had radiographic evidence of a pulmonary infiltrate. One hundred and twelve children (23.3%) required oxygen treatments and 13 (2.7%) were transferred to the ICU. Multivariable logistic regression showed that compared with the ≤6 months children, those aged >60 months old had shorter hospital stay (OR = 0.45); children with oxygen treatment tended to have longer hospital stays than those without oxygen treatment (OR = 2.14). The mean cost of each influenza-related hospitalization was US$ 624 (US$ 1323 for children referred to ICU and US$ 617 for those cared for on the wards). High risk children had higher total cost than low-risk patients.

Conclusion

Compared to other countries, in Suzhou, children hospitalized with influenza have longer hospital stay and higher percentage of pneumonia. The direct medical cost is high relative to family income. Effective strategies of influenza immunization of young children in China may be beneficial in addressing this disease burden.

Clinical characteristics of pediatric hospitalizations associated with 2009 pandemic influenza A (H1N1) in Northern Bavaria, Germany

Background

The 2009 pandemic influenza A (H1N1) (PIA) virus infected large parts of the pediatric population with a wide clinical spectrum and an initially unknown complication rate. The aims of our study were to define clinical characteristics and outcome of pandemic influenza A (H1N1) 2009-associated hospitalizations (PIAH) in children <18 years of age. All hospitalized cases of children <18 years of age with laboratory-confirmed pandemic influenza A (H1N1) 2009 in the region of Wuerzburg (Northern Bavaria, Germany) between July 2009 and March 2010 were identified. For these children a medical chart review was performed to determine their clinical characteristics and complications.

Results

Between July 2009 and March 2010, 94 PIAH (62% males) occurred in children <18 years of age, with a median age of 7 years (IQR: 3–12 years). Underlying diseases and predisposing factors were documented in 40 (43%) children; obesity (n = 12, 30%), asthma (n = 10, 25%) and neurologic disorders (n = 8, 20%) were most frequently reported. Sixteen (17%) children received oxygen supplementation; three (3%) children required mechanical ventilation. Six (6%) children were admitted to an intensive care unit, four of them with underlying chronic diseases.

Conclusions

Most PIAH demonstrated a benign course of disease. However, six children (6%) needed treatment at an intensive care unit for severe complications.