Case Report
Infection of immunocompromised patients by avian H9N2 influenza A virus

https://doi.org/10.1016/j.jinf.2011.02.007Get rights and content

Summary

Avian influenza A (H9N2) virus is transmitted sporadically from avian species to human causing mild diseases in immunocompetent person. We report two cases of human infection in immunocompromised patients in Hong Kong between 2008 and 2009. One patient had uneventful recovery with viral shedding at day 10 after symptom onset despite her underlying acute lymphoblastic leukaemia. The other patient with post-bone marrow transplant chronic graft-versus-host disease and bronhioltis obliterans went into respiratory failure. Genetic analysis revealed that these cases were caused by different genetic variants which are circulating in poultry in this region. Review of literature identified another 9 human cases reported in Southern China since 1988. It is possible that human infection with H9N2 is more common than what has been recognized. Continuous surveillance of H9N2 influenza virus infection in human is warranted.

Introduction

Since the first documentation of human infection with the highly pathogenic avian influenza A (H5N1) virus in 1997 resulting in 18 hospitalizations and 6 deaths,1 a series of infection control measures to prevent viral transmission from poultry to human have been implemented in the Hong Kong Special Administrative Region, China. These included a monthly moratorium, or rest day with cleansing of all the poultry stalls in order to interrupt the viral replication cycle and reduce the viral load in the poultry markets.2 Live ducks and geese, natural reservoirs of avian influenza viruses, were not allowed in the markets because of their potential of asymptomatic viral shedding. Biosecurity measures were tightened in local farms such as using bird-proof nets to prevent the spread of virus from migratory birds to poultry. Active immunization of chickens from local and crossed border farms with H5 vaccines and randomly taken cloacal swabs from chickens for H5 detection by RT-PCR before transferring them to the wet markets were performed.2 These measures have successfully prevented the occurrence of newly acquired human cases of avian influenza H5N1 in the locality since 1997. However these measures were unable to stop the endemicity of avian influenza A H9N2 in our poultry population.

The H9N2 virus is another major subtype of avian influenza virus which has been prevalent among domestic poultry in Asia since the early 1990s.3, 4, 5, 6 As routine immunization in poultry against this subtype of virus is not a common practice, the persistence of the virus in poultry markets may be the source of the sporadic human infections in southern China since 1998.7, 8 Three human cases of avian influenza A (H9N2) have been reported in Hong Kong between 1999 and 2003.9, 10 All of them were children with uncomplicated influenza-like illness and fully recovered. Serological analysis in a limited number of humans in Southern and Northern China found that about 1% of the tested subjects had antibodies against the H9 subtype haemagglutinin.11, 12 It is unclear whether human infection with H9N2 influenza is in fact more common than that which has been reported. Here, we described 2 cases of avian influenza A (H9N2) infection in immunocompromised patients and reviewed the relevant English and Chinese literatures on culture confirmed cases of human infections of avian influenza A (H9N2).

Section snippets

RT-PCR assay

Total nucleic acid was extracted from 250 μl of nasopharyngeal aspirate (NPA) using NucliSens easyMAG instrument (bioMerieux, NC, US) according to the manufacturer’s instructions. RT-PCR targeting the M gene of influenza A and subtype was performed as previously described.13 In the conventional 1-step RT-PCR assay for H9, a forward primer 5′-TGR TGT ATG CCC CAC ATG AA-3′ and a reverse primer 5′-TTG CTC CAC ACA GAG CAC AAT-3′ was used to amplify the haemagglutinin gene and generated a fragment

Case 1

In late December 2008, a 3-month-old girl was admitted to the general paediatric unit of Tuen Mun Hospital in Hong Kong for influenza-like illness with cough, nasal obstruction, and vomiting. She resided in Shenzhen, Guangdong, China with her mother and had a history of contact with live poultry at a local restaurant before symptom onset. NPA was positive for influenza A virus by rapid antigen test (Directigen EZ Flu A + B, Becton Dickinson). She was aferible during hospitalization and was

Discussion

Southeast Asia has always been considered as an epicentre for emerging novel influenza viruses over the past 40 years, including the pandemic influenza viruses in 1957 and 1968, the avian influenza A (H5N1) virus in 1997, and many new variants of seasonal influenza viruses.14 The avian influenza A (H9N2) virus is one of the major subtypes of influenza viruses and has been adapted to land-based poultry in this region. It is therefore not surprising that all of the reported cases of human avian

Acknowledgement

The study is partly funded by the Providence Foundation Limited in memory of the late Dr. Lui Hac Minh and the Research Fund for the Control of Infectious Diseases (RFCID) of the Food and Health Bureau and Research Grants Council of the Hong Kong Special Administrative Region, China (HKU 7488/05M, 7500/06M and HKU 7619/07M).

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