*3.2.1 Dengue virus*

Dengue virus (DENV) is a single-stranded RNA virus, enveloped by a bilayer lipid membrane. The premembrane (prM) protein and envelope glycoprotein adhere to the membrane. Dengue virus can infect humans through mosquito bites. Symptoms, that include high fever, severe headache, muscle and joint pain, nausea, vomiting, swollen lymph nodes and rash, usually appear 3–14 days post-infection [139]. Most patients will recover in 2–7 days, while a small number of patients' conditions may worsen accompanied by bleeding, thrombocytopenia and plasma protein effusion. Up to 22,000 people die from Dengue annually and currently there are no therapies to treat this infection [140].

Ulipristal, a FDA approved small molecule, is an elective progesterone receptor modulator (SPRM), that has been demonstrated to be a potent inhibitor of DENV, most likely by blocking viral entry [141]. The antiviral activity was evaluated by *in vitro* DENV infection assay using Vero E6 cells. The results show that ulipristal has an antiviral effect against DENV in Vero E6 cells with an EC50 of 8.3 ± 0.1 μM. The anti-DENV effect of ulipristal was further confirmed using a murine infection model. The ulipristal-treated group presented less weight loss and disease symptoms compared the control group. A significant drop was also detected in the degree of viremia in the blood of the ulipristal-treated group. This study showed that ulipristal has desirable anti-DENV effects *in vitro* and *in viv*o [141].
