Syphilis Increases HIV Viral Load and Decreases CD4 Cell Counts

Recent outbreaks of syphilis among men who have sex with men in major US cities, and reported increases in sexual risk behavior, have generated concerns about the potential increases in HIV incidence associated with these syphilis epidemics.

Syphilitic ulcers are known to facilitate the transmission of HIV infection, but the effect of syphilis infection on HIV viral loads and CD4 cell counts is poorly understood.

Researchers abstracted medical records for HIV-infected male syphilis patients seen at three clinics in San Francisco and Los Angeles from January 2001 to April 2003. They compared plasma HIV-RNA levels and CD4 cell counts during syphilis infection with those before syphilis infection and after syphilis treatment, using the Wilcoxon signed rank test.

Results

Fifty-two HIV-infected men with primary or secondary syphilis had HIV viral load and CD4 cell count data available for analysis; 30 (58%) were receiving antiretroviral therapy.

Viral loads were higher during syphilis compared with pre-syphilis levels by a mean of 0.22 RNA log10 copies/ml (P = 0.02) and were lower by a mean of -0.10 RNA log10 copies/ml (P = 0.52) after syphilis treatment.

CD4 cell counts were lower during syphilis infection than before by a mean of -62 cells/mm3 (P = 0.04), and were higher by a mean of 33 cells/mm3 (P = 0.23) after syphilis treatment.

Increases in the HIV viral load and reductions in the CD4 cell count were most substantial in men with secondary syphilis and those not receiving antiretroviral therapy.

Conclusion

In conclusion, the authors write, “Syphilis infection in HIV-infected men was associated with a significant increase in the HIV viral load and a significant decrease in the CD4 cell count.”

“Because of the overlap in risk behaviors that lead to HIV and syphilis infections, and because syphilis may enhance HIV transmission via the syphilitic ulcers and by raising the HIV viral load, integrated public health efforts to prevent new syphilis infections, and to identify and treat syphilis cases promptly, are warranted to reduce the spread of both diseases within affected communities.

From the Epidemic Intelligence Service, Division of Applied Public Health Training, Epidemiology Program Office, Division of HIV/AIDS Prevention, National Center for HIV, STD and TB Prevention, and Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA; STD Program, Los Angeles County Department of Health Services, Los Angeles, CA, USA; STD Prevention and Control Services, City and County of San Francisco, San Francisco, CA, USA, and Department of Medicine, University of California in San Francisco, San Francisco, CA, USA.

10/15/04

Reference
K Buchacz and others. Syphilis increases HIV viral load and decreases CD4 cell counts in HIV-infected patients with new syphilis infections.
AIDS 18(15): 2075-2079, October 21, 2004.