Two clusters of human infection with influenza A/H5N1 virus in the Republic of Azerbaijan, February–March 2006

Abstract

Following the appearance of influenza A/H5 virus infection in several wild and domestic bird species in the Republic of Azerbaijan in February 2006, two clusters of potential human avian influenza due to A/H5N1 (HAI) cases were detected and reported by the Ministry of Health (MoH) to the World Health Organization (WHO) Regional Office for Europe during the first two weeks of March 2006. On 15 March 2006, WHO led an international team, including infection control, clinical management, epidemiology, laboratory, and communications experts, to support the MoH in investigation and response activities. As a result of active surveillance, 22 individuals, including six deaths, were evaluated for HAI and associated risk infections in six districts. The investigations revealed eight cases with influenza A/H5N1 virus infection confirmed by a WHO Collaborating Centre for Influenza and one probable case for which samples were not available. The cases were in two unrelated clusters in Salyan (seven laboratory confirmed cases, including four deaths) and Tarter districts (one confirmed case and one probable case, both fatal). Close contact with and de-feathering of infected wild swans was considered to be the most plausible source of exposure to influenza A/H5N1 virus in the Salyan cluster, although difficulties in eliciting information were encountered during the investigation, because of the illegality of some of the activities that might have led to the exposures (hunting and trading in wild birds and their products). These cases constitute the first outbreak worldwide where wild birds were the most likely source of influenza A/H5N1 virus infection in humans. The rapid mobilisation of resources to contain the spread of influenza A/H5 in the two districts was achieved through collaboration between the MoH, WHO and its international partners. Control activities were supported by the establishment of a field laboratory with real-time polymerase chain reaction (RT-PCR) capacity to detect influenza A/H5 virus. Daily door-to-door surveillance undertaken in the two affected districts made it unlikely that human cases of influenza A/H5N1 virus infection remained undetected.

What is the evidence of a role for host genetics in susceptibility to influenza A/H5N1?

“…Families live together in intimate contact and personto-person transmission has been convincingly put forward as an explanation for two family clusters [37,38] and an additional five reports have stated that it could not be ruled out in at least seven families [3,4,[39][40][41]. The evidence for person-to-person transmission outside of the family is mixed.…”

Zoonotic Risk for Influenza A (H5N1) Infection in Wild Swan Feathers

“…In 2006, human infections of influenza A (H5N1) of avian origin were found in the Republic of Azerbaijan [3]. Epidemiological investigation revealed seven cases including four fatalities that were possibly linked to wild swans infected with the virus [3].…”

“…Epidemiological investigation revealed seven cases including four fatalities that were possibly linked to wild swans infected with the virus [3]. The most probable source for human infection was defeathering of dead wild swans for making pillows [3].…”

“…Combined with migrating behavior, the high susceptibility to the AI virus (H5N1) and the virus shedding from infected swans are of great concern in terms of virus transmission to distant places [2,4,5,11]. Moreover, wild swans have been considered as direct sources for human influenza A (H5N1) infections in the Republic of Azerbaijan, which was the first suspected occurrence of people contracting the disease from wild birds [3].…”

Two clustered cases of confirmed influenza A(H5N1) virus infection, Cambodia, 2011

“…Clusters of confirmed human cases have been described in the past in Azerbaijan [2], mainland China [3], Egypt [4], Hong Kong [5], Indonesia [6], Pakistan [7,8] Thailand [9], Turkey [10] and Vietnam [11]. In at least one Indonesian cluster, transmission of A(H5N1) may have occurred through contact with environmentally-contaminated material [12].…”