After being infected with the HIV virus, 50% to 70% of people will experience symptoms similar to a cold, such as fever, headache, sore throat, muscle and joint pain, occasional nausea, vomiting, diarrhea, swollen lymph nodes, and skin rashes, all occurring around half a month later. Of course, some people may not exhibit any symptoms at all. If symptoms do appear, they generally disappear within a month. At this time, it is necessary to conduct a screening test between the first and second month. If necessary, another screening test can be performed in the third month to determine whether there is an HIV infection.