Hi.. Can understand your concern... As per your complain thrush is a fungal infection caused by fungus known as Candida Albicans.. Thrush is not a viral infection and it is caused by fungus and not virus.. Thrush usually develops suddenly that is within a day or two after exposure to fungus or when the fungal proliferation increases as fungal infection is an opportunist infection and can occur where ever body has deficient resistance to infection like due to some immune deficiency conditions or long term intake of some medication,dry mouth etc.. In case you had an unprotected sex one and a half year back then the fungal infection doesn t seems to be because of that nd it can be due to some other cause like taking long term steroids,antibiotics ,birth control medicines. It can occur in case of HIV,uncontrolled diabetes,dry mouth, direct contact with infected individuals etc.. In case if you have thrush and do not find any other condition as causative for thrush you should get checked for Diabetes.. A proper treatment oral intake of antifungal agents like Fluconazole,Itraconazole and topical application of Anti fungal ointments and following of precautionary measures can help in complete resolution of the thrush in a short period of time.. Hope this information helps.. If you find the answer helpful kindly write a positive review and click on found this answer helpful as a token of appreciation.. Thanks and regards.. Dr.Honey Nandwani Arora.