It is not necessary to have many sexual partners to be infected with a disease, but if you do not know whether your partner has a disease, the increase in the number of sexual partners in this case will increase the probability of being infected with a disease. Because the health status of each partner is not well known, it is possible that he or she carries or has a sexually transmitted disease, and it is more likely to be transmitted if one has more partners. If your partner is free of any sexually transmitted diseases, you will not be able to transmit any sexually transmitted diseases to yourself even if you have more partners. So, this is a case by case basis. But in the actual situation, the health status of the sexual partner is generally not very clear, as far as possible or fixed sexual partners, in order to prevent from being infected with the disease to the greatest extent.