ArticlesTransmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands
Introduction
On March 1, 2003, the Dutch Ministry of Agriculture announced a ban on the export of all poultry and poultry-related products. This measure was taken in response to outbreaks of a disease highly lethal to chickens on six farms in the province of Gelderland, an area with a high density of poultry farms. The infection spread to 255 farms, and the Ministry's order for the culling of all infected flocks led to the killing of around 30 million chickens—about 28% of the total chicken population in the Netherlands. The annual export value of poultry and eggs contributes €284 millionto the Dutch economy every year.
The pathogen was identified as a highly pathogenic avian influenza A virus (HPAI) subtype H7N7, and was related to viruses detected in 2000 during routine surveillance of avian influenza in ducks in the Netherlands. All internal genes of the viruses were of avian origin.1 Epizootics and solitary infections of A/H7N7 avian influenza virus in poultry have been reported in surveillance studies, and humans were thought to be at low risk of infection, although there have been occasional reports of H7N7-associated conjunctivitis.2, 3, 4 In 1996, influenza A/H7N7 virus (A/England/ 268/96) was isolated from a 43-year-old duck owner with mild one-sided conjunctivitis.4, 5
In the week following the announcement of the avian influenza outbreak, four independent anecdotal reports suggested an increased incidence of health complaints, particularly conjunctivitis, in people involved in the control of the epizootic. Coincidentally, data from routine influenza virus surveillance suggested a late seasonal increase in the rate of human influenza viruses. With the almost simultaneous confirmation of an influenza virus A/H7N7-associated conjunctivitis and human influenza virus A/H3N2 in two different veterinarians involved in control measures for the HPAI epizootic, physical prevention measures were reinforced and we began vaccination and actively seeking out people with symptoms?ie, cases.
Here, we describe the epidemiological and virological results of our case finding and the preventive measures taken to control the outbreak in human beings.
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Study organisation
After the first confirmation of chicken-to-human transmission of influenza A/H7N7, an outbreak investigation team was assembled at the RIVM (Rijksinstituut voor Volksgezondheid and Milieu [National Institute of Public Health and the Environment]). The population at risk was defined as the group of people living or working in the Netherlands after February 28, 2003, who had direct contact with poultry or poultry products that could have been infected with H7, or who had close contact with an
Case finding
On March 5, 2003, a veterinarian who visited several farms with HPAI-infected poultry flocks developed acute conjunctivitis. The symptoms in the first eye started 30 h after his last farm visit; within the next 24 h, similar problems arose in the other eye. Eye swabs collected about 60 h after the onset of symptoms were positive for influenza A/H7 by RT-PCR and tissue culture. On the basis of these findings, active case finding was started from March 10, 2003.
By June 9, 2003, 453 people who
Discussion
We describe a large outbreak of avian influenza A/H7 in human beings, with 89 infected people, of whom 85 fitted case definitions of conjunctivitis or influenza-like illness. Conjunctivitis was noted as the prevailing symptom in three secondary cases, confirming the predilection of these viruses for the eye.
That influenza-like symptoms were reported less often by A/H7-positive cases than other cases suggests that the influenza A/H7 viruses do not cause influenza-like illness. Alternatively, the
References (30)
- et al.
Avian influenza virus isolated from a woman with conjunctivitis
Lancet
(1996) - et al.
Infection of children with avian-human reassortant influenza virus from pigs in Europe
Virology
(1994) - et al.
Genetic reassortment between avian and human influenza A viruses in Italian pigs
Virology
(1993) - et al.
Seroepidemiological evidence of avian H4, H5, and H9 influenza A virus transmission to pigs in southeastern China
Vet Microbiol
(2002) - et al.
Emergence of H3N2 reassortant influenza A viruses in North American pigs
Vet Microbiol
(2000) Influenza A (H5N1) in Hong Kong: an overview
Vaccine
(2002)- et al.
Human influenza A H5N1 virus related to a highly pathogenic avian influenza virus
Lancet
(1998) - et al.
Human infection with influenza H9N2
Lancet
(1999) - et al.
Characterization of a human H9N2 influenza virus isolated in Hong Kong
Vaccine
(2001) - et al.
The 1999–2000 avian influenza (H7N1) epidemic in Italy: veterinary and human health implications
Acta Trop
(2002)
Clinical features and rapid viral diagnosis of human disease associated with avian influenza A H5N1 virus
Lancet
Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome
PNAS
Recent zoonosis caused by influenza A viruses
Rev Sci Tech
Conjunctivitis in human beings caused by influenza A virus of seals
N Engl J Med
Characterisation of an avian influenza A virus isolated from a human—is an intermediate host necessary for the emergence of pandemic influenza viruses?
Arch Virol
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