Treatment training manual

5. 3 OI and coinfection overview

In 2023, most OIs are seen in people who are diagnosed late. This is when the CD4 count is already low.

This is sometimes when less than 350 cells/mm3 but mainly if less than 200 cells/mmor even lower.

HIV treatment (ART) is now effective at reducing the risk of nearly all OIs. For anyone diagosed with an OI, starting ART is usually as important as any direct OI treatment.

In a few cases, the OI needs to be treated first with ART starting soon after.

For this basic course, it is important to learn about the OIs that are most common in your country. In countries where ART is now widely used and earlier diagnosis is improving, many OIs are more rare.

There are about ten main OIs that advocates should know about.

There are at least another ten other important OIs that are less common.

What to find out about an OI

Type of infection

  • Is the OI caused by a virus, bacteria, parasites or a fungus etc?
  • How is the OI acquired and how to avoid it?
  • Is the OI infectious to other people? If so, how?

Main symptoms

  • What are the symptoms (signs of illness)?

Symptoms help identify OIs. Sometimes symptoms are enough to start treatment, based on a ‘best guess’ (called empirical treatment).

Many OIs have the similar symptoms.

Most OIs can cause primary disease in a range of organs.


  • How is the infection confirmed by tests?

This usually means either testing blood, saliva or sputum (fluid from the lungs). It can involve trying to grow a culture from one of these samples (which can take several weeks).

A definite diagnosis can be difficult or impossible. You may only know if the suspected illness was identified correctly if symptoms improve after treatment.


  • How is the illness treated? Are there choices?
  • What is the success rate for treatment?
  • Can treatment be stopped afterwards?

Most OIs, but not all of them, resolve after successful treatment for HIV. This is because ART has enable the CD4 counts to rise.


  • Is treatment useful to prevent infection in the first place?
  • At what CD4 count can prophylaxis be stopped?
  • Are there different recommendations in different countries?

Prophylaxis means taking treatment to prevent an illness.

Secondary prophylaxis is where you continue a treatment after the illness is better to prevent it occurring again.


  • Are better tests or drugs being developed that could help in the future?

Links and further reading

Last updated: 1 January 2023.