Ratio of CD4+ to CD8+ T-Cells in the recent reported cases of bird flu infection in Asia.

Abstract

Influenza is an infectious disease caused by a constantly varying RNA virus. Influenza A virus is a naturally occurring infection in different animals including humans, pigs, horses, sea mammals, mustelids and birds (1). Capua and Alexander reviewed the sudden emergence of different strains of influenza A virus transmissible to humans, termed antigenic shift, which had occurred on four occasions, 1918 (H1N1), 1957 (H2N2), 1968 (H3N2) and 1977 (H1N1), each time resulting in a pandemic (1). In 1997, a new potentially devastating influenza pandemic occurred in Hong Kong, 18 cases of influenza (bird flu) caused by a novel H5N1 (chicken) influenza virus resulted in death of six individuals (2). Webster noted that separation of aquatic birds from domestic poultry in Hong Kong after the H5N1 bird flu incident could influence the interspecies transmission of influenza viruses (3). In the year 2004, H5N1 infection reemerged in Southeast Asia. Thailand and Vietnam are the two countries endemically hit by this infection. Since January 2004, the bird flu has been detected in some poultry farms and the Thai and Vietnam governments have launched several attempts to control the infection (1, 4). During the outbreak, there were some reports of human infection causing severe disease with high mortality rate reported from Vietnam and Thailand (1, 4). Most infected patients developed progressive pneumonia with progressing and acute respiratory distress syndrome (ARDS) and died subsequently (1, 4). Some hematologic abnormalities were noted in patients with bird flu, the main one of which was lymphopenia with decreased lymphocyte neutrophil ratio (5). Anemia was also observed in this infection (6). However, the immunohematological aspect of this viral infection has not been well documented. Here, we performed this mini-study in order to document the impact of bird flu infection on CD4/CD8 ratio, a marker of immune depletion, as reported for patients in Thailand and Vietnam. We hypothesized that the change in CD4 and CD8 cell counts in patients infected with H5N1 strain might be similar to general influenza infection (7).