Increased Number of Human Cases of Influenza Virus A(H5N1) Infection, Egypt, 2014–15

During November 2014–April 2015, a total of 165 case-patients with influenza virus A(H5N1) infection, including 6 clusters and 51 deaths, were identified in Egypt. Among infected persons, 99% reported poultry exposure: 19% to ill poultry and 35% to dead poultry. Only 1 person reported wearing personal protective equipment while working with poultry.

H ighly pathogenic avian influenza virus A(H5N1) has been detected among poultry in >60 countries, with sporadic transmission to humans that results in a large number of deaths (1). Of 842 persons with H5N1 virus infection reported as of June 23, 2015, worldwide, 447 (53%) died (2,3). During November 2014-February 2015, the Egyptian Ministry of Health (MoH) surveillance systems identified an unprecedented number of persons with severe respiratory illness caused by infection with H5N1 virus. These illnesses occurred during months when seasonal influenza is typically epidemic in Egypt (4). In response, the MoH initiated an investigation into potential causes of the increased number of cases.
Persons meeting the ILI case definition have fever >38°C and >1 of the following: cough, dyspnea, sore throat, myalgia, and body aches. Persons meeting the ILI case definition are admitted, and respiratory samples are collected for influenza testing.
Technicians at 8 sentinel sites also collected daily respiratory samples from 2 patients meeting the ILI case definition and from all patients admitted with severe acute respiratory infection, defined as hospitalization occurring within 2 weeks of onset of fever and cough. Nasal and oropharyngeal swabs were transported to Egypt's National Influenza Center for testing by reverse transcription PCR (2). For patients testing positive for H5N1, MoH staff visited their households; administered a standardized questionnaire to obtain demographic, exposure, clinical, and treatment information; and searched among patient contacts for additional case-patients.
We  Almost all (163/165) case-patients during 2014-15 had exposure to domestic poultry 1-2 weeks before symptom onset; 58% were involved in breeding, 24% in slaughtering, and 21% in preparing poultry. Most (115/165 [70%]) were exposed at home; 4% recalled exposure in shops, 3% at live bird markets, and 1% at farms. Although 35% recalled exposure to dead birds and 19% to ill birds, 35% recalled exposure only to birds that appeared healthy. One case-patient reported wearing personal protective equipment when working with poultry.

Conclusions
Our analyses suggest that H5N1 infections have recurred annually in Egypt during November-April. Although MoH identified an unprecedented number of H5N1 case-patients during 2014-15, the proportion of persons testing positive was similar to proportions of previous epidemic seasons. During 2006-2015, the Ministry of Agriculture identified 3,273 outbreaks among poultry, primarily during Egypt's November-April winter months (1). One study found that ≈2% of Egyptians exposed to poultry were seropositive for H5N1 virus (5). The large number of H5N1 case-patients identified during 2014-15 could result in part from increased respiratory sampling in communities with poultry outbreaks, rather than from marked changes in the virus's transmission characteristics.
The H5N1 case-patients during the 2014-15 season had similar characteristics to those of previous seasons (6). Nearly all had recent exposure to domestic poultry (7). Active surveillance from 2010-2012 suggests that 8% of healthy-appearing poultry in Egypt were infected with H5N1 clade 2.2.1 (8), yet only 1 case-patient in 2014-15 reported using personal protective equipment. Human H5N1 infections have been shown to occur during poultry outbreaks, overlapping with October-December influenza epidemics (4). Egypt currently recommends seasonal influenza vaccination among health care workers, pregnant women, persons with chronic diseases, and Hajj and Umrah travelers. Countries where seasonal influenza overlaps with H5N1 circulation in poultry might explore the feasibility of vaccinating persons at high risk for influenza co-infections and complications (9).
After identification of case-patients in Egypt, officials investigated contacts. This strategy perhaps enriched the number of H5N1 case-patients identified during peak epidemic months, compared with randomly selecting persons meeting case definitions for respiratory illnesses. Although we did not find increased rates of persons testing positive for H5N1, all H5N1 case-patients are unlikely to have the  same probability of being identified (i.e., contacts vs. randomly selected persons). Egypt continues to have substantial H5N1 circulation among poultry. Although the characteristics of case-patients during 2014-15 were similar to those of previous seasons and do not suggest increased efficiency of H5N1 transmission between humans, MOH would be warranted in examining H5N1 virus circulating in Egypt for genomic markers of mammalian adaptation (10), which have been identified since 2010 (11), and in using a cross-sectoral approach to evaluate interventions to prevent H5N1 infections.