Interim estimates of the effectiveness of influenza vaccination against influenza-associated hospitalization in children in Hong Kong, 2015-16.

From 1 September 2015 through 31 January 2016, we enrolled 2068 children 6 months to 17 years of age admitted to hospital with a febrile acute respiratory infection in our test-negative study. Information on receipt of 2015-16 northern hemisphere inactivated influenza vaccination was elicited from parents or legal guardians. Using conditional logistic regression adjusting for age and matching on calendar time, we estimated influenza vaccine effectiveness against hospitalization with influenza A or B to be 79.2% (95% confidence interval: 42.0%-92.4%). Annual influenza vaccination should be more widely used in children in Hong Kong.

The Dynamic Relationship Between Clinical Symptomatology and Viral Shedding in Naturally Acquired Seasonal and Pandemic Influenza Virus Infections.

BACKGROUND: Although the pattern of viral shedding over time has been documented in volunteer challenge studies, understanding of the relationship between clinical symptomatology and viral shedding in naturally acquired influenza infections in humans remains limited. METHODS: In a community-based study in Hong Kong from 2008 to 2014, we followed up initially healthy individuals and identified 224 secondary cases of natural influenza virus infection in the household setting. We examined the dynamic relationship between patterns of clinical symptomatology and viral shedding as quantified using reverse transcription polymerase chain reaction and viral culture in 127 cases with a clinical picture of acute respiratory infection. RESULTS: Viral shedding in influenza A virus infections peaked on the first 1-2 days of clinical illness, and decreased gradually to undetectable levels by day 6-7, matching closely with the dynamics of clinical illness. Viral shedding in influenza B virus infections rose up to 2 days prior to symptom onset and persisted for 6-7 days after onset with a bimodal pattern. CONCLUSIONS: Our results suggest that while clinical illness profiles may serve as a proxy for clinical infectiousness in influenza A virus infections, patients may potentially be infectious even before symptom onset or after clinical improvement in influenza B virus infections.

Adenovirus respiratory infection in hospitalized children in Hong Kong: serotype-clinical syndrome association and risk factors for lower respiratory tract infection.

Lower respiratory tract infections (LRTI) caused by adenovirus can be severe with resultant chronic pulmonary sequelae. More than 50 serotypes have been recognized; however, the exact association of serotype with clinical phenotype is still unclear. There have been no reports on the adenovirus serotype pattern in Hong Kong, and their relationships with disease manifestations and complications are not known. Clinical and epidemiological data on 287 children (<6 years old) admitted with adenovirus respiratory infections from 2001 to 2004 were reviewed. Common presenting symptoms included fever (97.9 %) and cough and rhinitis (74 %). Extra-pulmonary manifestations were present in 37.3 %. The clinical picture mimicked bacterial infection for its prolonged high fever and neutrophilic blood picture. Forty-two patients (14.6 %) had LRTI, either pneumonia or acute bronchiolitis, but none had severe acute respiratory compromise. Children aged 1 to 2 years old were most at risk for adenovirus LRTI (adjusted p = 0.0165). Serotypes 1 to 7 could be identified in 93.7 % of the nasopharyngeal specimens, with serotypes 2 and 3 being the most prevalent. Different serotypes showed predilection for different age groups and with different respiratory illness association. The majority of acute bronchiolitis (71.4 %) were associated with serotype 2 infection, and this association was statistically significant (p < 0.0001). Serotype 3 infection accounted for over half of the pneumonia cases (57-75 %) in those aged 3-5 years old. Only one patient developed mild bronchiectasis after serotype 7 pneumonia. Children aged 1 to 2 years old were the at-risk group for adenovirus LRTI, but respiratory morbidity was relatively mild in our locality. There was an apparent serotype-respiratory illness association.

Systems-level comparison of host responses induced by pandemic and seasonal influenza A H1N1 viruses in primary human type I-like alveolar epithelial cells in vitro.

BACKGROUND: Pandemic influenza H1N1 (pdmH1N1) virus causes mild disease in humans but occasionally leads to severe complications and even death, especially in those who are pregnant or have underlying disease. Cytokine responses induced by pdmH1N1 viruses in vitro are comparable to other seasonal influenza viruses suggesting the cytokine dysregulation as seen in H5N1 infection is not a feature of the pdmH1N1 virus. However a comprehensive gene expression profile of pdmH1N1 in relevant primary human cells in vitro has not been reported. Type I alveolar epithelial cells are a key target cell in pdmH1N1 pneumonia. METHODS: We carried out a comprehensive gene expression profiling using the Affymetrix microarray platform to compare the transcriptomes of primary human alveolar type I-like alveolar epithelial cells infected with pdmH1N1 or seasonal H1N1 virus. RESULTS: Overall, we found that most of the genes that induced by the pdmH1N1 were similarly regulated in response to seasonal H1N1 infection with respect to both trend and extent of gene expression. These commonly responsive genes were largely related to the interferon (IFN) response. Expression of the type III IFN IL29 was more prominent than the type I IFN IFNß and a similar pattern of expression of both IFN genes was seen in pdmH1N1 and seasonal H1N1 infection. Genes that were significantly down-regulated in response to seasonal H1N1 but not in response to pdmH1N1 included the zinc finger proteins and small nucleolar RNAs. Gene Ontology (GO) and pathway over-representation analysis suggested that these genes were associated with DNA binding and transcription/translation related functions. CONCLUSIONS: Both seasonal H1N1 and pdmH1N1 trigger similar host responses including IFN-based antiviral responses and cytokine responses. Unlike the avian H5N1 virus, pdmH1N1 virus does not have an intrinsic capacity for cytokine dysregulation. The differences between pdmH1N1 and seasonal H1N1 viruses lay in the ability of seasonal H1N1 virus to down regulate zinc finger proteins and small nucleolar RNAs, which are possible viral transcriptional suppressors and eukaryotic translation initiation factors respectively. These differences may be biologically relevant and may represent better adaptation of seasonal H1N1 influenza virus to the host.

Rhinovirus infection in hospitalized children in Hong Kong: a prospective study.

OBJECTIVES: To analyze the clinical features and estimate the hospitalization disease burden of rhinovirus infection in children in Hong Kong. METHODS: In this prospective study, nasopharyngeal aspirates were taken from children aged <18 years with symptoms of acute respiratory infection admitted to Queen Mary Hospital on one fixed day of the week during August 2001-July 2002 for detection of common respiratory viruses by immunofluorescence, viral culture, and for rhinovirus, human metapneumovirus, and coronaviruses by reverse transcription polymerase chain reaction. The clinical features of rhinovirus infections were analyzed and hospitalization disease burden was estimated. RESULTS: Altogether 239 of the 426 nasopharyngeal aspirates (56.1%) were positive for respiratory viruses, including 151 patients with rhinovirus (35.4%). The median age was 2.34 years. Upper respiratory infection, asthma exacerbation, pneumonia, and acute bronchiolitis were diagnosed in 44.4%, 19.9%, 11.3%, and 7.9%, respectively. The most common symptoms were cough (81.5%), runny nose (76.8%), and fever (68.9%). Shortness of breath, wheezes, and crepitation were present in 25.8%, 29.1%, and 18.5%, respectively. Fifty-five of 99 patients (55.6%) had chest radiographic abnormalities, most commonly perihilar streakiness. Children with chronic diseases were more likely to have lower respiratory tract infection and these children required longer hospitalization (mean 0.6 days longer). Coinfection with other respiratory pathogens was common (33.1%). CONCLUSION: Rhinovirus is frequently associated with asthmatic exacerbations and lower respiratory tract infection, especially in children with chronic diseases and is potentially an important contributor to hospitalization in children in Hong Kong.

Risk for infection with highly pathogenic influenza A virus (H5N1) in chickens, Hong Kong, 2002.

We used epidemiologic evaluation, molecular epidemiology, and a case-control study to identify possible risk factors for the spread of highly pathogenic avian influenza A virus (subtype H5N1) in chicken farms during the first quarter of 2002 in Hong Kong. Farm profiles, including stock sources, farm management, and biosecurity measures, were collected from 16 case and 46 control chicken farms by using a pretested questionnaire and personal interviews. The risk for influenza A (H5N1) infection was assessed by using adjusted odds ratios based on multivariate logistic regression analysis. Retail marketing of live poultry was implicated as the main source of exposure to infection on chicken farms in Hong Kong during this period. Infection control measures should be reviewed and upgraded as necessary to reduce the spread of influenza A (H5N1) related to live poultry markets, which are commonplace across Asia.

Infants born to mothers with severe acute respiratory syndrome.

Severe acute respiratory syndrome (SARS) is a newly discovered infectious disease caused by a novel coronavirus. During the community outbreak in Hong Kong, 5 liveborn infants were born to pregnant women with SARS. A systematic search for perinatal transmission of the SARS-associated coronavirus, including serial reverse transcriptase-polymerase chain reaction assays, viral cultures, and paired serologic titers, failed to detect the virus in any of the infants. In addition, none of the infants developed clinical, radiologic, hematologic, or biochemical evidence suggestive of SARS. One preterm infant developed jejunal perforation and another developed necrotizing enterocolitis with ileal perforation shortly after birth. This case series is the first report to describe the clinical course of the first cohort of liveborn infants born to pregnant women with SARS.