There is no cure for HIV, but a person who reaches and maintains an undetectable viral load through treatment cannot sexually transmit the virus to others. This is known as undetectable = untransmittable (U=U).

HIV is a virus that weakens the immune system and increases the risk of contracting other infections and diseases.

HIV attacks CD4 cells, a type of white blood cell that usually helps the body fight infections. HIV overtakes CD4 cells to create more copies of itself, destroying the host cell. This allows the virus to spread while weakening the body’s immune system.

Some people may develop symptoms 2–4 weeks after contracting HIV. These acute symptoms may last for a few days to a few weeks. They can include:

  • fever
  • tiredness
  • rash
  • muscle aches
  • sore throat
  • swollen glands in the throat, groin, or armpit
  • nausea, vomiting, or both

HIV can worsen without treatment and cause additional complications. For instance, HIV can progress to stage 3 HIV, also called AIDS, where the immune system is severely damaged. People with this late stage are vulnerable to many infections that can be life threatening.

Doctors use blood tests to check for the presence and severity of HIV. One of these tests checks viral load. It measures how many copies of HIV are present in a milliliter (mL) of blood.

People with HIV typically have a detectable viral load before they start treatment. Treatment aims to reduce the viral load as much as possible, which doctors call viral suppression.

There is currently no cure for HIV. However, treatment can lead to an undetectable viral load. This is when the virus is present in such small quantities that it causes few problems and does not sexually transmit to others.

Keep reading to learn more about undetectable viral loads.

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The Centers for Disease Control and Prevention (CDC) states that viral suppression is when someone has under 200 copies of HIV per mL of blood.

Different ways of testing blood for HIV mean that laboratories may have different definitions for what viral load is undetectable.

However, 2021 research suggests that people with fewer than 200 copies of HIV per mL of blood can live long and healthy lives, and not sexually transmit the virus to others.

The main goal of treatment is to reach and maintain an undetectable viral load.

Antiretroviral therapy (ART) involves taking several drugs that prevent HIV from replicating. These medications reduce the viral load to give the immune system a chance to produce more CD4 cells and fight off infections.

ART drugs cannot completely remove HIV from the body. However, reducing the viral load to undetectable levels effectively prevents someone from sexually transmitting HIV. People must continue taking daily ART drugs to maintain an undetectable viral load.

People undergoing ART typically receive a viral load test after starting treatment. A doctor generally recommends testing for viral load every 4–8 weeks, or more often if a person has a later stage of the condition.

People experiencing symptoms or health issues related to HIV should start improving after reaching an undetectable viral load. At that point, the immune system is typically strong enough to fight off infections and diseases.

Some people with HIV may be unable to reach an undetectable viral load. This may include people taking other medications that interact with ART. In these cases, people require additional precautions and health checkups.

Many people receiving ART can maintain an undetectable viral load and live long and healthy lives. However, there are still some things for a person to keep in mind about their undetectable status.

Even if undetectable, people can still get other STIs

HIV treatment does not protect against other sexually transmitted infections (STIs), so it does not decrease a person’s ability to get other STIs. Because HIV compromises the immune system, it can make getting other STIs more likely.

Certain STIs have a closer link to HIV than others. These include:

For a person who maintains an undetectable viral load, having another STI does not increase their risk of transmitting HIV to a sexual partner. However, ART for HIV does not stop a person from transmitting other STIs.

HIV can be transmitted via sharing needles to inject drugs

People can also transmit HIV through other practices involving an exchange of bodily fluids, such as sharing needles and syringes.

According to the CDC, 1 in 10 new HIV diagnoses in the United States are related to injection drug use.

The CDC states that it remains unclear whether people with undetectable viral loads can still transmit the virus by sharing needles and syringes.

To help manage the risk, some communities offer syringe services programs (SSPs). These programs give people new needles and help them dispose of used ones.

Undetectable HIV can become detectable

A person with HIV can maintain an undetectable viral load with treatment. However, if treatment stops, HIV will accumulate and become detectable again.

People with undetectable viral loads must continue taking ART. The drugs suppress HIV to protect the immune system.

Stopping or reducing ART gives the virus a chance to accumulate and weaken the immune system again.

A person may still need to use condoms if they are undetectable

Even if a person has an undetectable viral load, the CDC recommends they continue to use condoms or other barrier methods to limit the transmission of other STIs.

The CDC states there is effectively no risk of someone with an undetectable viral load sexually transmitting HIV.

However, it is still possible to transmit other STIs, such as:

Experts recommend people with an undetectable viral load still follow safe sex practices. The American College of Obstetricians and Gynecologists suggests people can reduce the risk of STIs by:

  • knowing their sexual partners
  • using condoms or other barrier methods
  • being aware of the increased risk of certain sexual practices, such as anal sex
  • getting vaccinated against hepatitis B and HPV

If a person has an undetectable viral load and wishes to breastfeed or chestfeed, they can talk with a doctor about how to do this safely.

According to the CDC, receiving ART and maintaining an undetectable viral load reduces the chances of transmission through breastfeeding to less than 1%.

Below are some frequently asked questions about undetectable HIV.

Can a person catch HIV from someone who is undetectable?

There is no risk of contracting HIV sexually from a person who has an undetectable viral load. This is referred to as undetectable = untransmittable (U=U).

How long can a person live with undetectable HIV?

A person who has undetectable HIV and maintains an undetectable viral load via daily antiretroviral therapy (ART) drugs will have a normal life expectancy.

Can a person stay undetectable forever?

A person with HIV can maintain an undetectable viral load with daily antiretroviral therapy (ART).

Even with treatment, however, they may experience small, temporary increases in viral load followed by a decrease back to undetectable levels. These are known as blips and are relatively common.

If treatment stops altogether, HIV will accumulate and become detectable again.

An undetectable viral load is when the number of HIV copies is too low for blood tests to detect. Antiretroviral treatment aims to reach and maintain an undetectable viral load.

When HIV is well managed, people have a lower risk of contracting other infections, such as opportunistic infections. They are also able to have sex with no risk of transmitting HIV to others. However, it is still important to practice safe sex to reduce the risk of transmitting other STIs.