Syphilis and HIV infections are both risk factors for one another. Additionally, people who have HIV and syphilis are at a greater risk of developing a more serious form of syphilis. However, scientists do not yet know how to optimize syphilis treatments for those with HIV.

This article discusses the link between syphilis and HIV. It looks at how each disease impacts the risk of developing the other.

It also examines the connection between syphilis and HIV viral load, the progression of syphilis, the treatment and diagnosis of syphilis with HIV, and outlook.

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Syphilis is a bacterial sexually transmitted infection (STI). It arises due to an infection from the Treponema pallidum bacterium.

According to the Centers for Disease Control and Prevention (CDC), 176,713 people had syphilis in the United States in 2021.

The CDC indicates there were 36,136 new HIV diagnoses in the United States in 2021. Unlike syphilis, HIV is a viral STI.

However, it is also possible for an individual to have both syphilis and HIV.

Learn more about bacterial infections.

There is strong anecdotal scientific evidence that having syphilis increases the probability of contracting HIV.

According to a systematic review and meta-analysis from 2021, having syphilis may triple an individual’s probability of developing HIV. The review authors arrived at this figure by analyzing medical records from over 65,000 people.

Several phenomena may explain these results. For instance, people with syphilis can develop genital ulcers, which may make HIV transmission easier.

Scientists continue to research why syphilis is a risk factor for HIV.

According to a 2020 population-based study in Taiwan, having HIV can also increase the probability of developing syphilis. It is unclear why this association exists. It is strongest among specific demographics, such as younger males.

Learn whether HIV is an STI.

An individual’s HIV viral load is the amount of HIV in their blood.

According to an older study, evidence shows that people with HIV may have an above-average HIV viral load if they have syphilis. corroborates these results based on several other studies.

These findings may help to explain why people with syphilis are at an increased risk of HIV.

Learn more about an HIV viral load.

According to, syphilis does not often progress any differently among people with HIV than in people without HIV. However, some evidence shows that HIV can cause an unusual presentation of syphilis in certain individuals.

Syphilis usually begins as a single painless nodule that typically ulcerates quickly. Doctors call this the primary stage of syphilis.

It is more common for people with HIV to develop multiple painful ulcerated nodules. However, some people with HIV do not develop nodules during the primary stage of syphilis.

Secondary syphilis often involves a rash, which can affect entire sections of the body. It usually appears after the primary-stage nodules have disappeared.

However, there is an increased risk that someone with HIV will have symptoms of primary and secondary syphilis at the same time.

The evidence also suggests that syphilis can progress more rapidly in people with compromised immune systems, such as with HIV.

When syphilis becomes advanced, it can affect important organ systems.

Learn about syphilitic meningitis, a complication of syphilis.

According to the CDC, doctors diagnose syphilis using blood tests, which detect signs of past or current infection based on bacteria antibodies.

In the United States, at least 18 specific tests exist. One type of test is the rapid plasma reagin test.

Learn about some at-home syphilis tests.

Anecdotal reports indicate that HIV may potentially worsen the outlook of people with syphilis.

However, the CDC states no convincing evidence exists for the efficacy of syphilis treatment regimens in people with HIV.

Scientists do not seem to know how to reduce the risk of syphilis progression in people with HIV without relying on standard forms of treatment, such as antiretroviral therapy (ART).

ART may reduce syphilis progression because it prevents the development of HIV. However, scientists need to do more more research to confirm this.

When someone has syphilis and HIV, doctors treat these conditions separately.

According to, the mainstay of treatment is ART. Doctors can successfully treat primary and secondary syphilis with benzathine penicillin G. This is an antibiotic drug. For more advanced cases of syphilis, doctors may prefer antibiotics such as crystalline penicillin G.

Learn more about how ART works.

Syphilis and HIV are both serious conditions. Without treatment, each can be fatal.

Research suggests that doctors find it more challenging to manage syphilis and HIV co-infections than to manage each infection on its own. There is also evidence that the co-existence of syphilis and HIV is increasing.

Learn about life expectancy for people with HIV.

Having HIV can increase the risk of developing syphilis. The reverse is also true. This may be because people with syphilis have an above-average HIV viral load if they do contract HIV. Additionally, ulcerated sores in syphilis might increase the likelihood of an HIV infection.

Doctors treat HIV with specific medications that slow the progression of the disease. They treat syphilis with antibiotics. At present, there is no specific treatment for syphilis in people with HIV.

Evidence indicates that HIV can worsen the outlook for people with syphilis by encouraging it to develop into its more advanced stages.

HIV and AIDS resources

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