Human-to-human transmission of avian influenza A/H7N7, The Netherlands, 2003

Abstract

An outbreak of highly pathogenic avian influenza A virus subtype H7N7 began in poultry farms in the Netherlands in 2003. Virus infection was detected by RT-PCR in 86 poultry workers and three household contacts of PCR-positive poultry workers, mainly associated with conjunctivitis. To determine the magnitude of and risk factors for human-to-human transmission of influenza A/H7N7 in the Netherlands, a retrospective cohort study among household members of infected poultry workers was undertaken. In total, 33 (58.9%) of 56 (among 62) participants who provided blood samples had positive H7 serology, using single convalescent serum samples obtained at least 3 weeks after onset of symptoms of the index case. Eight household members (12.9%) reported symptoms (conjunctivitis and/or ILI), of which four of five (80.0%) tested seropositive. On univariate analysis, significant risk factors for seropositivity included having at least two toilets, a pet bird, and using cloth handkerchiefs. It was not possible to obtain a stable model for binomial regression for the outcome of A/H7N7 infection. Further seroprevalence studies among contacts of asymptomatic H7 cases should be conducted.

Pandemic influenza planning: Shouldn’t swine and poultry workers be included?

“…recently documented several clusters of human-to-human swine influenza virus infections [20]. Similarly, although likely rare, there have been a number of reports of human-to-human transmission of highly pathogen avian influenza virus infections [25][26][27]. Infected with a virus efficient in human-to-human transmission, such agricultural workers would like serve as bridging population to infect their families and possibly their medical care providers.…”

Protective measures and human antibody response during an avian influenza H7N3 outbreak in poultry in British Columbia, Canada

“…12,14 Antibody to the H7 subtype could not be found in the sera of exposed people by routine hemagglutination inhibition assay but was detected in half of 500 people tested by a modified hemagglutination inhibition approach. 13,[15][16][17] Between Feb. 17 and May 18, 2004, an outbreak of avian influenza due to an H7N3 subtype occurred among poultry in the Fraser Valley of British Columbia, Canada. The source of the virus was never determined.…”

“…These, however, were not confirmed by microneutralization assay. 13,[15][16][17] We performed multiple retrospective assays, including modified hemagglutination inhibition, without further yield. Given the uncertainties in serologic assays for avian influenza, caution should be applied in the interpretation of serologic results.…”

“…21 On Mar. 16 and Mar. 24, 2 workers experienced onset of mild unilateral conjunctivitis (the first accompanied by coryza, the second by headache) following separate incidents of direct conjunctival contact with infected poultry during culling operations on Mar.…”

Adapting global influenza management strategies to address emerging viruses

“…Because these virus strains widely circulate in wild fowl and domestic poultry, most of the human infections coincided with poultry outbreaks. Historically, these infections have caused mild upper respiratory symptoms, with the exception of one death in the Netherlands (19). Unlike these prior outbreaks, the current H7N9 has a much higher rate of human lethality in comparison.…”