Human disease from influenza A (H5N1), Thailand, 2004

Abstract

Influenza A (H5N1) is endemic in poultry across much of Southeast Asia, but limited information exists on the distinctive features of the few human cases. In Thailand, we instituted nationwide surveillance and tested respiratory specimens by polymerase chain reaction and viral isolation. From January 1 to March 31, 2004, we reviewed 610 reports and identified 12 confirmed and 21 suspected cases. All 12 confirmed case-patients resided in villages that experienced abnormal chicken deaths, 9 lived in households whose backyard chickens died, and 8 reported direct contact with dead chickens. Seven were children <14 years of age. Fever preceded dyspnea by a median of 5 days, and lymphopenia significantly predicted acute respiratory distress syndrome development and death. Among hundreds of thousands of potential human cases of influenza A (H5N1) in Asia, a history of direct contact with sick poultry, young age, pneumonia and lymphopenia, and progression to acute respiratory distress syndrome should prompt specific laboratory testing for H5 influenza.

Figure 1

Epidemic curve showing the dates of onset for 12 confirmed and 21 suspected human cases of avian influenza A (H5N1) infection, Thailand, 2004.

Figure 2

Distribution of the absolute lymphocyte count (ALC), total leukocyte count, and platelet count on admission for 4 patients who survived and 8 who died of human influenza A (H5N1) infection, Thailand, 2004. ARDS, acute respiratory distress syndrome.

Figure 3

Chest radiographs from patients 8 and 9. Panel A demonstrates patchy alveolar infiltration of the right lower lung on day 5 of illness for patient 9; panel B demonstrates the progression to acute respiratory disease syndrome (ARDS) on day 8. Panel C shows interstitial infiltration of both lungs of patient 8 on day 4 of illness; panel D shows the rapid progression to ARDS by day 6.

Figure 4

Timing of the clinical course and oseltamivir treatment for 4 patients who survived and 8 patients who died of human influenza A (H5N1) infection, Thailand, 2004.

Figure 5

Pathologic findings from a patient (number 6) with confirmed influenza A (H5N1) infection. All slides are stained with hematoxylin and eosin, shown at 40x objective. Panel A shows hyaline membrane formation lining the alveolar spaces of the lung and vascular congestion with a few infiltrating lymphocytes in the interstitial areas. Reactive fibroblasts are also present. Panel B is an area of lung with proliferating reactive fibroblasts within the interstitial areas. Few lymphocytes are seen, and no viral intranuclear inclusions are visible. Panel C shows fibrinous exudates filling the alveolar spaces, with organizing formation and few hyaline membranes. The surrounding alveolar spaces contain hemorrhage. Panel D is from a section of spleen, showing numerous atypical lymphoid cells scattered around the white pulp. No viral intranuclear inclusions are seen.

Figure 6

Seasonal variation in viral isolations of human influenza A (H3N2), A (H1N1), and B, in Thailand.