Acute HIV-1 Infection in Two Women Over 50 Years Old: Diagnostic Challenges and Clinical ImplicationsKey Clinical Message (KCM)： In-depth analysis of these two cases reveals the importance of HIV1-RNA in the diagnosis of patients with acute HIV infection, as well as the importance of highly sensitive P24 antigen and antibody reagents in early screening.Abstract: This report details two cases of acute HIV-1 infection in women aged 51 and 52 years. Both patients presented with nonspecific symptoms (diarrhea or fatigue) following high-risk sexual behavior. Initial fourth-generation HIV antigen/antibody screening (Mike Bio Co., Ltd.) yielded indeterminate results (Case 1: 7.359 S/CO; Case 2: 1.093 S/CO; reference <1.000 S/CO), while HIV-1 Western blot assays returned negative. Subsequent HIV-1 RNA quantification (COBAS®) confirmed high viral loads (Case 1: 12,663,500 copies/mL; Case 2: 1,451,731 copies/mL). These cases underscore three critical points: (1) the diagnostic necessity of nucleic acid testing in acute HIV infection, particularly during the serological window period; (2) the limitations of relying solely on Western blot confirmation in early infection; and (3) the growing epidemiological significance of HIV in older women. These findings highlight the importance of integrating high-sensitivity p24 antigen/antibody assays with RNA testing for timely diagnosis and clinical management.Key words: HIV-1 RNA,HIV-1 Western blot, acute HIV infection1.IntroductionAcquired Immune Deficiency Syndrome (AIDS), a chronic infectious disease caused by the Human Immunodeficiency Virus (HIV), remains one of the most significant global public health challenges. HIV primarily spreads through sexual contact, blood transfusions, and mother-to-child transmission. AIDS is divided into three stages: acute infection, asymptomatic infection and AIDS. The acute infection stage, occurring 4-6 weeks post-HIV infection, presents with characteristic symptoms including fever, general malaise, headache, nausea, sore throat, myalgia, arthralgia, rash, and cervical/occipital lymphadenopathy. Despite its clinical significance, this early stage is frequently overlooked, potentially impacting the disease’s subsequent progression and management. Recent epidemiological studies reveal concerning trends in HIV/AIDS prevalence and disease burden. Global data from 1990 to 2019 demonstrate an increasing number of people living with HIV/AIDS and rising age-standardized prevalence rates. Notably, female patients exhibit higher age-standardized disability-adjusted life years (DALYs), years lived with disability (YLDs), and years of life lost (YLLs) compared to male patients, indicating a greater disease burden among women[1, 2].In China, the period from 2010 to 2022 witnessed a significant epidemiological shift, with a continuous rise in HIV infections among individuals aged 50 years and older. Particularly striking is the dramatic increase in HIV prevalence among women in this age group, rising from 16.26% in 2010 to 62.78% in 2022 - a rate substantially higher than their male counterparts[3].This upward trend highlights the need for intensive attention and targeted interventions for HIV prevention in women aged 50 years and older. This report details two illustrative cases of early acute HIV infection in middle-aged and elderly women. By conducting an in-depth analysis of these cases, we aim to improve clinical diagnostic accuracy, promote timely and effective treatment initiation, and offer valuable insights for the development and refinement of public health prevention and control strategiesCase ReportCase 1, female, 51 years old, met a man in a square dance in July 2024, and then had sex in the hotel (a total of two or three times), without the consciousness of wearing a condom. In early September, she developed fever and diarrhea for 4+ days with no obvious cause, 10+ times/day, yellow watery stool, maximum body temperature of 39.2℃, and was hospitalized in a local hospital for treatment (specific drug use is unknown), with no obvious relief of symptoms. For further diagnosis and treatment, she was admitted to the Department of Infectious Diseases of our hospital as ”acute gastroenteritis” in the outpatient department. Preliminary laboratory examination showed that the white blood cell count was 2.17*109/L(normal 3.5-9.5 *109/L),Lymphocyte count 0.91*109/L(normal 1.1-3.2 *109/L), AST:58 IU/L (normal 13-35 IU/L), TP:57g/L (normal 65-85 g/L), ALB:34g/L(normal 40-55 g/L), AFU36U/L (normal 10-35 U/L), indicating impaired liver function, preliminary assessment of leukopenia, abnormal liver function.On September 8, 2024, the preliminary screening of the fourth-generation antigen/antibody (Mike Bio CO., LTD.) test showed that HIV infection was to be determined, HIVAg/Ab7.359 S/CO (normal <1.000S/ Co), and the HIV-1 Western blot test of the sample was negative 5 days later. However, the sample tested positive for HIV-1 RNA（COBAS） molecules 13 days later, with a result of 12,663,500 copies/m(Fig1), confirming the screening results. On September 29, blood samples were taken again for the absolute count of T lymphocyte subsets. The absolute count of CD4 was 531cell/ul, lower than the lower limit of reference, and the absolute count of CD8 was 2493cell/ul, higher than the upper limit of reference. The CD4/CD8 ratio was 0.21, lower than the lower limit of reference.