A method for determining, in vitro, the probability of a patient developing severe dengue, based on a blood sample, in which: a) the quantity in the blood sample of at least one marker, which is platelet factor 4, is determined； b) the quantity of platelet factor 4 determined in step a) is compared with a reference quantity of the marker obtained from a group of individuals who have been diagnosed with non-severe dengue, wherein, if the quantity of platelet factor 4 determined in step a) is less than the reference quantity established in step b), it is determined that the patient will develop severe dengue.
