Asthma is a common chronic respiratory disease and an important global public health problem.The asthma mortality was decreasing worldwidely, but varied among countries.The mortality of asthma in children and young people aged 0-19 years in China was at a low level in the world, ranging from 0.023/100 000 to 0.046/100 000.The overall trend was downward from 2008 to 2018, with the lowest mortality rate of 0.023/100 000 in 2018.However, due to the large population in China, the estimated death numbers of asthma in children and young people was relatively high (70-148 persons per year). Most of deaths caused by asthma were avoidable.Inadequate implementation of asthma action plan is one of the important risk factors of death caused by asthma.Learning experiences and lessons of asthma management from other countries, and improving self-management of asthma are important to achieve the goal of asthma control and reduce the death of children with asthma.

In 2021, the World Asthma Day theme is " Uncovering Asthma Misconceptions" . It provides a call to action to address common widely held myths and misconceptions concerning asthma that prevent persons with asthma from optimal benefit from the major advances in the management of this condition.In the long-term management of asthma, asthma action plan is the most important tool of self-management and can convey asthma knowledge and correct misconceptions to children with asthma and their families.In order to promote implementation of asthma action plan, " Expert consensus on clinical application of Chinese Children′s Asthma Action Plan" and " One hundred key issues on Chinese Children′s Asthma Action Plan " will be published in this journal, providing clinical guidance for formulating individualized asthma action plan, and detailed explanations of asthma action plan-related questions, so as to convey the true conceptions of asthma, reduce and prevent asthma attacks, prevent asthma-related deaths and improve self-management of children with asthma.

In March 2009,a new influenza A H1N1 virus was identified in Mexico.It is a quadruple-reassortant influenza A virus, which is composed of a combination of swine, avian strains and human. The clinical symptoms of the 2009 new influenza A (H1N1) are similar with the seasonal influenza.The severe illness could happened in youth and middle-aged without underlying diseases that differs from seasonal influenza. The risk groups are individuals with underlying diseases,pregnancy and obesity which has not been considered as risk factor in previous. Although oseltamivir-resistant variant influenza A ( H1N1 ) were reported, strain is susceptible to oseltamivir. This review summarizes the current information concerning viral genom,clinical features and treatment of the new pandemic influenza virus A H1N1 infection.

The Ebola virus haemorrhagic fever outbreak began in Guinea and other West Africa countries in Feb.2014.Its high mortality cause worldwide attention.What is Ebola virus? What is its epidemiological characteristics and clinical manifestations? As pediatric medical workers,what should we do? The hot issues at present will be discussed in this article.

Pulmonary vascular disease is a group of diseases,defined as the dysfunction of pulmonary artery,pulmonary vein and pulmonary capillary.Pulmonary vascular disease includes pulmonary hypertension,pulmonary vascular malformation,pulmonary vasculitis and pulmonary vascular thrombosis,et al.The manifestations of pulmonary vascular disease vary from recurrent wheezing,respiratory tract infection,short of breath and hemoptysis,et al.With the development of radiography investigations,the diagnosis of pulmonary vascular disease is improved.Pulmonary vascular disease in children is not uncommon therefore we should focus on it.

Hemoptysis,defined as the expectoration of blood or blood-tinged sputum from the lower respiratory tract has to be differentiated from hematemesis and other anatomic site of bleeding.In pediatric patients with hemoptysis,no definite classification correlating severity with blood loss exists.Thus,clinical judgment is the primary tool that clinicians have in assessing the severity of hemoptysis in children.Infection is one of the most common etiologies for hemoptysis in children; however,cystic fibrosis was the most common cause of pediatric hemoptysis in the European countries.Hemoptysis is not a common chief complaint in pediatric patients unless massive hemoptysis.The causes of massive hemoptysis in children are bronchial adenoma,bronchial foreign body and vascular abnormalities.Vascular abnormalities is rare cause of hemoptysis,but one of the common cause of massive hemoptysis,including pulmonary arteriovenous malformation,absent pulmonary valve,aberrant systemic artery supplying.As one of aberrant systemic artery supplying,bronchial artery-pulmonary artery malformation cause life-threatening hemoptysis.The aim of imaging evaluation is to identify the source of bleeding along with determination of the primary cause of hemoptysis.The initial management option for bronchial artery-pulmonary artery malformation is bronchial artery embolization.Surgery is alternative option.The patients with bronchial artery-pulmonary artery malformation usually have massive hemoptysis,which can quickly progress to acute respiratory distress and shock.Therefore these children require emergency procedures to stabilize.

The non-invasive positive-pressure ventilation(NPPV) play an important role in treating patient with upper airway obstructive diseases.The use of NPPV in children has significantly increased in recent years internationally.Nevertheless,the paediatric NPPV support in China was less reported.This review aimed to clarify the indications,efficacy and technical methods in NPPV,and therefore searched papers including clinical studies,reviews and guidelines focusing on children with upper airway obstructive diseases who were treated on NPPV.The review concluded that NPPV is a treatment choice for patient who has upper airway obstruction and can not be solved by surgery.The NPPV avoids the impairment to the body caused by recurrent hypoxemia and arousals,decreases the rate of intubation and improves the quality of life.NPPV need to be preformed in a professional children's medical center.Education and training for the parent is the key point of improving treatment compliance.

Hemophagocytic lymphohistiocytosis (HLH)is a severe syndrome characterised by fever,splenomegaly,cytopenia,hyperferritinemia,hypertriglyceridemia and hypofibrinogennemia.HLH includes primary and secondary HLH.Secondary HLH can be encountered in.association with a variety of underlying condtions.Infectious triggers are most commonly due to viral infections,especially EBV infection.This review mainly introduces clinical characteration of several viral infections associated HLH.

After primary EB virus(EBV) infection there are expansions of EBV-specific CD8~+/CD4~+ CTLs responses against lytic peptides and latent peptides in order to control EBV infection. Clinical manifestations of EBV infection are diverse.Its pathogenesis is not clear. The surveillance of EBV specific-immunity plays an important role to control viral replication.There are differences between the CTL responses against lytic peptides and latent peptides. And the migration and activation of EBV specific CTLs with different cell surface molecules play an important role in EBV infection .

Since Middle East respiratory syndrome( MERS)was first reported in 2012,the severe clinical symptoms and high mortality have been concerned. The epidemiology,possible pathogenesis,clinical manifestations(es-pecially in children),treatment and counter measures of MERS were reviewed in this paper.