title: Transient lymphopenia and neutropenia: pediatric influenza A/H1N1 infection in a primary hospital in Israel.
abstract: BACKGROUND
  Pandemic influenza A/H1N1 carries a relatively high morbidity, particularly in young people. Early identification would enable prompt initiation of therapy, thereby improving outcomes.
  
  
  OBJECTIVE
  To describe the epidemiological, clinical and laboratory characteristics of children admitted to hospital with the clinical diagnosis of influenza with reference to pandemic influenza A/H1N1.
  
  
  METHODS
  We conducted a prospective study of all children aged 16 years or less admitted to the pediatric department with the clinical diagnosis of influenza-like illness from July to October 2009. The presence of A/H1N1 virus was confirmed using real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis of nasopharyngeal secretions. Positive cases were compared with negative cases concerning epidemiological data, risk factors, clinical presentation and laboratory parameters, with emphasis on changes in the differential blood count.
  
  
  RESULTS
  Of the 106 study patients, 53 were positive to influenza A/H1N1 and 53 were negative. In both groups nearly all patients had fever at presentation and approximately two-thirds had both fever and cough. All patients had a mild clinical course, no patient needed to be admitted to the intensive care unit and no mortalities were recorded. Hyperactive airway disease was more common in the A/H1N1-positive group. Pneumonia occurred in 30% of children in both groups. Laboratory findings included early lymphopenia and later neutropenia in theA/H1N1-infected patients.
  
  
  CONCLUSIONS
  Leukopenia consisting of lymphopenia and later neutropenia was common in patients with A/H1N1 infection but was not correlated with disease severity or clinical course, which were similar in both groups. However, reduced leukocyte count can be used as an additional criterion for diagnosing A/H1N1 infection until RT-PCR results are available.
authors.affiliation: Department of Pediatrics, Laniado Hospital, Netanya, affiliated with Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel. nsharon@laniado.org.il
authors.forename: Nechama
authors.initials: N
authors.lastname: Sharon
authors.forename: Ruth
authors.initials: R
authors.lastname: Talnir
authors.forename: Ofri
authors.initials: O
authors.lastname: Lavid
authors.forename: Uri
authors.initials: U
authors.lastname: Rubinstein
authors.forename: Mark
authors.initials: M
authors.lastname: Niven
authors.forename: Yoel
authors.initials: Y
authors.lastname: First
authors.forename: Assaf J I
authors.initials: AJ
authors.lastname: Tsivion
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Schachter
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004279:DNA, Viral / Q000032:analysis; D004196:Disease Outbreaks; D006784:Hospitals, Teaching / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics*; D007251:Influenza, Human / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D007557:Israel / Q000453:epidemiology; D008231:Lymphopenia / Q000453:epidemiology / Q000209:etiology*; D009503:Neutropenia / Q000453:epidemiology / Q000209:etiology*; D011446:Prospective Studies; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004279:DNA, Viral