CD4 and infectious disease: WHO elucidated that patients that are coinfected with both HIV and TB are more prone to succumb to the tuberculosis disease and not only that but very sensitive to other infectious diseases which includes Pneumocystis jirovecii pneumonia because certain anti-drugs are dispensed to all HIV-positive patients including the ones that have CD4 count of 500 cells/ml, also to infants and as well as adults as post-exposure prophylaxis to HIV infection [113].