The significantly lower levels of haemoglobin observed among HIV-1 positive women (supplementary figure S1) is in agreement with earlier studies [35], [36], as well as the lower neutrophil counts which have been proposed by some authors as due to a direct infection of a neutrophil sub population expressing CD4 and CXCR4 surface markers [37]. The gene discussed is CXCR4; the disease is infection.