Please cite this paper as: Mak et al. (2012) The impact of pandemic influenza A (H1N1) 2009 on the circulation of respiratory viruses 2009–2011. Influenza and Other Respiratory Viruses 6(3), e6–e10.
...Surveillance of respiratory viruses has been conducted for many years at the public health laboratory in Hong Kong. With the occurrence of pandemic influenza A (H1N1) 2009, we observed a change in the seasonality of influenza activity with a seemingly corresponding change in the activity of respiratory syncytial virus, parainfluenza virus, and adenovirus during 2009–2011. This phenomenon could most likely be explained by virus interference.
Hepatitis E virus (HEV) is one of the major causes of acute and self-limiting hepatitis in human. In Hong Kong, the number of notifications increased from 26 to 62 from year 2001 to 2007. This study ...describes the molecular epidemiology of HEV in Hong Kong in order to determine the movement and distribution of HEV. HEV in 171 serum samples from HEV IgM positive cases from year 2001 to 2007 were amplified using RT-PCR and subjected to nucleotide sequencing. Phylogenetic analysis showed 162 of 171 HEV detected cases (94.7%) belonged to genotype IV and 8 (4.7%) to genotype I. Interestingly, a cluster of 10 cases in year 2007 that had the same sequence of HEV was identified. Epidemiological data however did not detect any relationship between these cases. Since zoonotic transmission is a well known route of HEV infection, close monitoring of the circulating HEV strains in human and food source animals may help to provide additional information on the transmission of HEV and possible source of infection in Hong Kong. J. Med. Virol. 81:1062-1068, 2009.
We conducted molecular analyses to confirm four clustering HIV-1 infections (Patient A, B, C & D) in Guangzhou, China. These cases were identified by epidemiological investigation and suspected to ...acquire the infection through a common heterosexual transmission chain.
Env C2V3V4 region, gag p17/p24 junction and partial pol gene of HIV-1 genome from serum specimens of these infected cases were amplified by reverse transcription polymerase chain reaction (RT-PCR) and nucleotide sequenced.
Phylogenetic analyses indicated that their viral nucleotide sequences were significantly clustered together (bootstrap value is 99%, 98% and 100% in env, gag and pol tree respectively). Evolutionary distance analysis indicated that their genetic diversities of env, gag and pol genes were significantly lower than non-clustered controls, as measured by unpaired t-test (env gene comparison: p < 0.005; gag gene comparison: p < 0.005; pol gene comparison: p < 0.005).
Epidemiological results and molecular analyses consistently illustrated these four cases represented a transmission chain which dispersed in the locality through heterosexual contact involving commercial sex worker.
In 1997, outbreaks of highly pathogenic influenza A (H5N1) among poultry coincided with 18 documented human cases of H5N1 illness. Although exposure to live poultry was associated with human illness, ...no cases were documented among poultry workers (PWs). To evaluate the potential for avian-to-human transmission of H5N1, a cohort study was conducted among 293 Hong Kong government workers (GWs) who participated in a poultry culling operation and among 1525 PWs. Paired serum samples collected from GWs and single serum samples collected from PWs were considered to be anti-H5 antibody positive if they were positive by both microneutralization and Western blot testing. Among GWs, 3% were seropositive, and 1 seroconversion was documented. Among PWs, ∼10% had anti-H5 antibody. More-intensive poultry exposure, such as butchering and exposure to ill poultry, was associated with having anti-H5 antibody. These findings suggest an increased risk for avian influenza infection from occupational exposure.
To establish whether human-to-human transmission of influenza A H5N1 occurred in the healthcare setting in Vietnam, we conducted a cross-sectional seroprevalence survey among hospital employees ...exposed to 4 confirmed and 1 probable H5N1 case-patients or their clinical specimens. Eighty-three (95.4%) of 87 eligible employees completed a questionnaire and provided a serum sample, which was tested for antibodies to influenza A H5N1. Ninety-five percent reported exposure to > or = 1 H5N1 case-patients; 59 (72.0%) reported symptoms, and 2 (2.4%) fulfilled the definition for a possible H5N1 secondary case-patient. No study participants had detectable antibodies to influenza A H5N1. The data suggest that the H5N1 viruses responsible for human cases in Vietnam in January 2004 are not readily transmitted from person to person. However, influenza viruses are genetically variable, and transmissibility is difficult to predict. Therefore, persons providing care for H5N1 patients should continue to take measures to protect themselves.
To determine virologically confirmed hospitalization rates associated with respiratory syncytial virus (RSV), adenovirus, and parainfluenza viruses in Hong Kong children.
All patients <18 years of ...age living on Hong Kong Island (within Hong Kong SAR) admitted for a febrile acute respiratory infection to 1 of the 2 public hospitals on 1 fixed day of the week between October 2003 and September 2006 were prospectively recruited. Hong Kong Island has a known population denominator and these 2 hospitals managed 72.5% of all general pediatric admissions for this population. Nasopharyngeal aspirates were tested for RSV, adenovirus, and parainfluenzae types 1, 2, and 3 by direct antigen detection and culture.
The annual hospitalization rate for RSV in infants <6 months of age was 233.4 to 311.2 per 10,000. Parainfluenza type 3 had a hospitalization rate of 27.3 to 122.8 per 10,000 in the 1 to <2 years group. Adenovirus was associated with significant hospitalization in those 6 months to 1 year (25.9-77.8 per 10,000), and in those 2 to <5 years (38.1-59.2 per 10,000). The mean duration of hospitalization for RSV was 4.04 ± 2.61 days, significantly longer than the 3.12 ± 1.41 days for adenovirus and the 2.93 ± 2.54 days for parainfluenza infections (P = 0.013 and P = 0.038, respectively).
We documented that the overall pediatric hospitalization burden of RSV was high and comparable to that of influenza. The burden for all the studied viruses was mainly in previously healthy children <5 years of age.
Two H9N2 viruses were isolated, for the first time, from humans in Hong Kong in 1999. Isolation of influenza viruses with a novel subtype of the hemagglutinin (HA) drew attention of health care ...authorities worldwide from the view of pandemic preparedness. Sequence analysis of the HA genes reveals that HA of A/Hong Kong/1073/99 (H9N2) is most closely related to that of A/quail/HK/G1/97 (H9N2) that contains the internal genes similar to those of Hong Kong/97 (H5N1) viruses. Phylogenetic and antigenic analyses demonstrated the diversity among H9 HA. A/Hong Kong/1073/99 was shown to cause a respiratory infection in Syrian hamsters, suggesting that the virus can replicate efficiently in mammalian hosts. We developed a whole virion test vaccine with a formalin-inactivated egg-grown HK1073. Intraperitoneal administration of the vaccine twice to hamsters conferred a complete protection against challenge infection by the MDCK cell-grown homologous virus. Receptor specificity of HK1073 appeared different from that of other avian influenza viruses of H9 subtype which recognize preferentially α-2,3 linked sialic acid. Hemagglutination of HK1073 with guinea pig erythrocytes was inhibited by both α-2,3 and α-2,6 linked sialic acid containing polymers. These data suggested that HK1073 had acquired a broader host range, including humans. Together with data so far available, the present study suggested that isolation of the H9 influenza viruses from humans requires precaution against the emergence of a novel human influenza.
To study the serologic response to the new pandemic influenza A (H1N1) 2009 virus in Hong Kong, the level of immunity was measured before and after the occurrence of the outbreak, and the titer of ...antibody to the pandemic influenza A (H1N1) 2009 virus in serum samples of laboratory confirmed cases. The presence of pre-outbreak pandemic influenza A (H1N1) 2009 virus antibodies in 37% of individuals older than >65 years suggested previous exposures to heterologous virus strains may have elicited cross-reacting antibody. Following large outbreaks of pandemic influenza A 2009 virus that peaked in September 2009, there is a change in immunity level in various age groups consistent with the attack rates among population in Hong Kong. Among individuals with mild clinical presentation, the antibody response to pandemic influenza A (H1N1) 2009 virus was stronger in those individuals aged less-than or equal to24 years but took more time to reach a titer of 40 when compared with those aged >24 years; however, the antibody level declined slower among individuals aged less-than or equal to24 years. Regardless of age, the antibody response rose rapidly and reached much higher titer among individuals with severe clinical presentation. Further study is required to collect additional data on antibody persistence and determine how much protection is conferred by previous exposure to seasonal influenza A (H1N1) viruses. J. Med. Virol. 82:1809-1815, 2010.
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