The World Health Organization declared that a new strain of novel swine-origin influenza A (H1N1) virus was responsible for the pandemic infection in June 2009. We report a case of encephalitis diagnosed as the H1N1 virus infection. We describe a 17-year-old patient who had a seizure attack, diagnosed with a H1N1 virus infection via real time reverse-transcriptase polymerase chain reaction (RT-PCR). The H1N1 virus infection can be causative of the encephalitis, as with other influenza virus infections. Careful monitoring is essential for reducing complications.
Adolescent ; Animals ; Encephalitis, Viral/*diagnosis/*virology ; Humans ; Influenza A Virus, H1N1 Subtype/*pathogenicity ; Male ; Swine/*virology

One 22-month-old boy who was admitted for a fever lasting 6 days as well as a cough and wheezing lasting 2 days was reported. He was diagnosed with influenza A (H1N1, severe type), severe pneumonia, acute respiratory distress syndrome (ARDS), Evans syndrome and multiple organ failure. This is the first case of novel influenza A (H1N1) and Evans syndrome. The pathogenesis is still unknown.
Anemia, Hemolytic, Autoimmune ; diagnosis ; Humans ; Infant ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; diagnosis ; virology ; Male ; Thrombocytopenia ; diagnosis

Since March 2009, pandemic A/H1N1/2009 influenza virus has been spreading throughout many countries including China. The emerged virus caused great harm to human health and social economy. Hemagglutinin (HA) is the most important viral surface glycoprotein, mainly possessing three kinds of functions: (1) binding to host cell receptor, (2) triggering the fusion between viral envelop and target cell membrane, (3) stimulating the body to generate the neutralizing antibody. Advances in the structure, primary function, evolution and antigenicity of pandemic A/H1N1/2009 influenza virus HA protein are reviewed in this paper.
Animals ; Evolution, Molecular ; Hemagglutinin Glycoproteins, Influenza Virus ; chemistry ; genetics ; immunology ; metabolism ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; immunology ; pathogenicity ; physiology ; Influenza, Human ; epidemiology ; virology ; Pandemics

BACKGROUNDSome research groups have hypothesized that human rhinoviruses (HRVs) delayed the circulation of the 2009 pandemic influenza A(H1N1) virus (A(H1N1)pdm09) at the beginning of Autumn 2009 in France. This study aimed to evaluate the relationship between HRV and A(H1N1)pdm09 in pediatric patients with influenza-like illness in Beijing, China.

METHODSA systematic analysis to detect A(H1N1)pdm09 and seasonal influenza A virus (FLU A) was performed on 4 349 clinical samples from pediatric patients with influenza-like illness during the period June 1, 2009 to February 28, 2010, while a one-step real-time RT-PCR (rRT-PCR) assay was used to detect HRV in 1 146 clinical specimens selected from those 4 349 specimens.

RESULTSDuring the survey period, only one wave of A(H1N1)pdm09 was observed. The percentage of positive cases for A(H1N1)pdm09 increased sharply in September with a peak in November 2009 and then declined in February 2010. Data on the monthly distribution of HRVs indicated that more HRV-positive samples were detected in September (2.2%) and October (3.3%), revealing that the peak of HRV infection in 2009 was similar to that of other years. Among the 1 146 specimens examined for HRVs, 21 (1.8%) were HRV-positive, which was significantly lower than that reported previously in Beijing (15.4% to 19.2%) (P < 0.01). Overall, 6 samples were positive for both A(H1N1)pdm09 and HRV, which represented a positive relative frequency of 1.60% and 2.08% HRV, considering the A(H1N1)pdm09-positive and -negative specimens, respectively. The odds ratio was 0.87 (95% CI 0.32; 2.44, P = 0.80).

CONCLUSIONSHRVs and A (H1N1)pdm09 co-circulated in this Chinese population during September and October 2009, and the HRV epidemic in 2009 did not affect A(H1N1)pdm09 infection rates in Beijing, China as suggested by other studies. However, the presence of A(H1N1)pdm09 might explain the unexpected reduction in the percentage of HRV positive cases during the period studied.

Child ; Child, Preschool ; China ; epidemiology ; Female ; Humans ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; epidemiology ; Male ; Picornaviridae Infections ; epidemiology ; Rhinovirus ; pathogenicity

This study aims to investigate the virological impact of the stalk region and cysteine (C) in neuraminidase (NA) of influenza A/Anhui/1/05 (H5N1) and A/Ohio/07/2009 (H1N1) viruses. The NA of A/ Anhui/1/05 (H5N1), defined as AH N1, lacked 20 amino acids (including C, defined as s20) as compared with NA of A/Ohio/07/2009 (H1N1) (defined as 09N1). We deleted s20 of 09N1 to construct 09N1-s20, and inserted s20 into AH N1 to construct AH N1+s20. To investigate the impact of C on the biological function of NA, we deleted C in 09N1 to construct 09N1-C and inserted C into AH N1 to construct AH N1-C. The pseudo-type viral particle (pp) system was used to evaluate the impact of these mutants on virology. The combination of 09N1-C and 09H1 (defined as 09H1::09N1-C) showed an infectivity 8 times that of the wild type 09H1::09N1, while the infectivity of the combination of AH N1+C and AH H5 (defined as AH H5::AH N1+C) was much lower than that of the wild type AH H5::AH N1. The infectivity of the combination of 09N1-s20 and 09H1 (defined as 09H1::09N1-s20) was 4 times that of the wild type 09H1::09N1; the infectivity of the combination of AH N1+s20 and AH H5 (defined as AH H5:: AH N1+s20) was 1/7 that of the wild type AH H5::AH N1. The co-existence of 09N1-C and AH H5 displayed 6 times the infectivity of AH H5::09N1, while the infectivity of 09H1::AH N1+C was very low. Multimer analysis showed that in the wild type 09N1, the forms of NA were dimer > tetramer > monomer; the major component of NA in 09N1-C was monomer; in 09N1-s20, the forms of NA were monomer > dimer. AH N1 was mainly composed of monomer; in AH N1+s20, the forms of NA were dimer > monomer > tetramer; in AH N1+C, the forms of NA were dimer > tetramer. Deletion of C or s20 from 09N1 did not change the expression of NA. The study suggested that deletion of C from the stalk region of NA in A/Ohio/07/2009 (H1N1) increases infectivity. Insertion of C into NA's stalk region of A/ Anhui/1/05 (H5N1) significantly decreases infectivity. Cysteine deletion in the stalk region is important for the infectivity of A/Anhui/1/05 (H5N1) and A/Ohio/07/2009 (H1N1). It may interfere with the infectivity via changes in NA polymerization.
Amino Acid Motifs ; Humans ; Influenza A Virus, H1N1 Subtype ; chemistry ; enzymology ; genetics ; pathogenicity ; Influenza A Virus, H5N1 Subtype ; chemistry ; enzymology ; genetics ; pathogenicity ; Influenza, Human ; virology ; Neuraminidase ; chemistry ; genetics ; metabolism ; Viral Proteins ; chemistry ; genetics ; metabolism ; Virulence

BACKGROUNDThe duration of viral shedding and the transmission of 2009 H1N1 influenza among individuals, especially among the younger population with mild illness, are not well understood now. The aim of this study was to determine the viral shedding of the young adult patients with mild 2009 H1N1 influenza in China.

METHODSFrom September 2009 to January 2010, the clinical data and serial nasopharyngeal swabs of 67 patients with 2009 H1N1 influenza and 37 patients with seasonal influenza aged from 18 years to 35 years were collected. The nasopharyngeal swab samples were detected by real time RT-PCR to determine the viral shedding. All the patients did not receive the antiviral therapy but Chinese medicine for detoxicating.

RESULTSAmong the patients with H1N1 virus infection, 82.1% (55/67) patients presented with fever symptom, while more patients with high fever (≥ 39°C) were found in seasonal influenza patients (P < 0.05). For the H1N1 patients, the median interval between the symptom onset and the undetectable RNA was six days (4 - 10 days). But viral shedding was still found in 31.3% patients after 7 days following illness onset. The median interval between disappearance of fever and an undetectable viral RNA level was three days (2 - 8 days), and 17.9% patients were found to be viral shedding 6 days later after normalization of body temperature. For the seasonal influenza patients, 94.6% patients were detected out viral RNA within 7 days. The median interval of seasonal influenza between the symptom onset and the undetectable RNA was four days (3 - 8 days). The median interval between disappearance of fever and an undetectable viral RNA level was three days (2 - 6 days).

CONCLUSIONIt suggests that 7 days isolation period from the illness onset or 24 hours after the resolution of fever and respiratory symptoms are not long enough to cut off the transmission among Chinese young adults with mild illness.

Adult ; Female ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; pathogenicity ; Influenza, Human ; epidemiology ; virology ; Male ; Real-Time Polymerase Chain Reaction ; Virus Shedding ; genetics ; physiology ; Young Adult

The clinical spectrum of the 2009 pandemic influenza A (H1N1) infection ranged from self-limited mild illness to progressive pneumonia, or even a fatal outcome. We summarize the clinical manifestations, risk factors for severe and fatal cases, pathologic findings and treatment of this disease in this paper based on current reports from different regions of the world.
Humans ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; complications ; epidemiology ; mortality ; pathology ; virology ; Pandemics ; Pneumonia ; epidemiology ; etiology ; mortality ; pathology ; Risk Factors

Adult ; Female ; Follow-Up Studies ; Humans ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; diagnosis ; Pregnancy ; Respiratory Distress Syndrome, Adult ; diagnosis ; virology

BACKGROUNDThe global outbreak of influenza A (H1N1) has led to the Ministry of Health of China listing it as one of the A-class infectious diseases. Pneumonia is the most serious complication of influenza A, commonly causing death. Populations are ordinarily susceptible to influenza A. This study aimed to investigate the imaging manifestation features of critical influenza A (H1N1) pneumonia and to improve its diagnostic techniques.

METHODSA total of seven death cases from critical influenza A (H1N1) pneumonia were retrospectively analyzed on their imaging manifestations and autopsy data. Pulmonary CT scanning was performed for five cases, with one receiving additional chest X-ray and chest CT scanning, and chest postero-anterior position X-ray examination was performed for other two. Autopsy was performed for five cases and postmortem examinations were performed for other two cases.

RESULTSThe seven cases of influenza A showed critical manifestations in 4 - 7 days after symptoms onset, with two having basic diseases of diabetes and one being pregnant. Extensive blurry high-density shadows of bilateral lungs were found in three cases, which were most obvious in middle and inferior parts of lungs. Pulmonary CT scanning revealed bilateral flaky parenchymal shadows in peripheral, dorsal and fundus segments of the middle-inferior parts of lungs, with one case of complicated pneumothorax, atelectasis and pleural effusion and another case of thin-walled cavity and dilated bronchi shadows in the superior parts of lungs.

CONCLUSIONSDiagnostic imaging is an important assessing tool for critical influenza A (H1N1) pneumonia. The imaging manifestations are characteristic instead of being specific. The definitive diagnosis can be made in combination with clinical examinations and laboratory tests.

Adolescent ; Adult ; Child ; Child, Preschool ; Female ; Humans ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; diagnosis ; diagnostic imaging ; virology ; Male ; Middle Aged ; Pregnancy ; Radiography ; Retrospective Studies ; Young Adult

BACKGROUNDIn early April 2009, cases of human infection with 2009 pandemic influenza A (H1N1) virus were identified in Mexico. The virus then spread rapidly to other regions of the world. From October 2009, sporadic imported cases of novel influenza A (H1N1) were continuously confirmed in Suzhou. The aim of the study was to review the chest CT findings in 63 patients with laboratory-confirmed novel swine-origin influenza A (H1N1) virus (S-OIV) infection.

METHODSChest CT examinations were collected from 63 S-OIV infected patients during their hospital stay. Three experienced radiologists inspected images to qualitatively and quantitatively characterize S-OIV induced image changes. CT scores of lesion severity were calculated based on the percentage of affected area to determine severity of infectious lesions. Patients were divided into two groups based on the leukocyte counts. Lesion patterns, local distributions, and quantitative measures were investigated and compared between the two groups.

RESULTSVarious degrees of bilateral multifocal lesions of ground-glass opacities were found with or without consolidations on the chest CT images. The lesions were both bronchocentric and centrilobular. Patients with elevated leukocyte counts had more extensive lesions, in terms of severity and affected area, than the patients with normal leukocyte counts. The lesion severity scores of patients in the elevated leukocyte group were significantly higher than those of the normal leukocyte group in terms of the entire lung area (P < 0.01), and upper (P < 0.05) and lower (P < 0.01) lobes as well. There were changes in the CT characteristics seen at follow-up as demonstrated by lesions absorption (P < 0.01), especially in the upper lobe of the lung (P < 0.01), but less so in the middle lobe/lingual and lower lobe of the lung (P > 0.05).

CONCLUSIONSThe most common CT findings in S-OIV infection patients were bilateral multifocal distributed ground-glass opacities and consolidations. The lesions were located dominantly at bronchocentric and centrilobular areas. Lung lesions were more obviously absorbed in upper lobes between two examinations. The observations and analysis from this study provide information that may be useful in image understanding and patient management for future pandemic influenza.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Child ; Child, Preschool ; Female ; Humans ; Influenza A Virus, H1N1 Subtype ; pathogenicity ; Influenza, Human ; diagnostic imaging ; virology ; Male ; Middle Aged ; Radiography ; Young Adult