A(H5N1) in two workers in Spain: suspected environmental contamination
On September 2022, two cases of avian influenza in humans were reported in Spain. Now the investigation of the incident is being published.
On 20 September 2022, an outbreak of HPAI A(H5N1) was confirmed in a poultry farm in the autonomous region of Castilla-La Mancha, Spain. Two days later, screening for influenza was performed on all 12 exposed workers. A nasopharyngeal swab from one worker, aged ca 20 years who was asymptomatic, was positive for influenza A by RT-PCR performed at the regional reference laboratory on 22 September. The presence of influenza A(H5N1) was confirmed by PCR by the Influenza National Reference Laboratory (NRL) on 27 September. After notification to the World Health Organization (WHO) on 4 October, a respiratory sample and an additional serum sample taken on 8 October were sent to the WHO Reference Laboratory (WRL) in London, United Kingdom yielding negative results for PCR detection and serology.
In response to the outbreak, culling of all hens at the farm was completed by 13 October and a new screening for influenza was conducted in all workers. This screening involved the initial 12 workers and 14 others who were involved in control tasks. A second asymptomatic worker in their late 20s tested positive for influenza A(H5N1) at the NRL. Samples for serology from this second worker were also taken on 19 October and 23 November. They were sent to the WRL and yielded a negative result.
Both workers were involved in egg collection and routine cleaning tasks. They used personal protection equipment, including an FFP2 mask, gloves, boots and an apron. After the outbreak confirmation, they helped in removal of dead hens, cleaning and disinfection of the premises, which ended on 22 October 2022.
The asymptomatic workers stayed in self-isolation, per the national protocol, from the first RT-PCR positive result until a second, negative, sample was obtained.
The absence of symptoms in both workers together with the laboratory results, which showed a very low viral load and the absence of specific H5 antibodies against the A/H5 virus, suggested that the positive results in the PCR were most likely due to environmental contamination. Of note, all samples (nasopharyngeal swabs) were taken outside the farm at a healthcare centre.
