How to Know If You Are at Risk for a Coinfection

Coinfection occurs when a host organism or cell is infected at the same time with more than one pathogen. While this can technically occur with many different combinations of infections, there are particular coinfections that commonly occur together related to various risk factors.

There are three particular conditions in which coinfections play a prominent role: Lyme disease, HIV, and hepatitis.

Lyme Disease

Lyme disease is considered a vector-borne disease. Vectors are anything that acts as a carrier of a disease. In the case of Lyme disease, ticks are the sole vector.

Ixodes ticks, also known as hard-bodied ticks, are one of the biggest culprits for transmitting vector-borne diseases. One of the most common types is Ixodes scapularis, also known as the deer tick, which is found in the northeastern, mid-Atlantic, and north-central United States. The western black-legged tick (Ixodes pacificus) is found on the Pacific Coast.

These ticks can themselves be infected with more than one disease-causing microbe. This becomes a problem when a coinfected tick bites a human and simultaneously transmits more than one infection. An Ixodes tick can transmit Borrelia burgdorferi, the bacterium that causes Lyme disease, along with one or more additional potentially serious illnesses.

In the U.S., the most common coinfections, particularly in people with chronic Lyme disease, are:

Symptoms of these infections can overlap with those of Lyme disease. These can include fever, chills, headaches, fatigue, and joint pain, which can complicate the diagnosis and also treatment.

Pathogens can also interact with one another. That's why if you have one or more coinfections with Lyme disease, you will likely exhibit more severe symptoms than someone who has only contracted Lyme disease.

Treating Lyme Disease Coinfections

Because it is often difficult to differentiate between Lyme disease and coinfections, your doctor may prescribe doxycycline, which treats Lyme disease and many other vector-borne diseases.

However, doxycycline may not be the best option for everyone, as it should be avoided in pregnant or nursing women as well as in children less than 8 years old. Other oral antibiotic options may include:

For more severe cases that warrant IV antibiotic administration, you may see the following medications used:

HIV Coinfections

Human immunodeficiency virus (HIV) attacks the body’s immune system by targeting certain white blood cells (CD4+ T cells) that are key to fighting infection. People with HIV are therefore vulnerable to a host of coinfections and their complications. Among the most common of these coinfections are:

  • Tuberculosis
  • Hepatitis B
  • Hepatitis C

Impact of HIV Coinfections

Tuberculosis (TB) poses a serious health risk for people with HIV. TB is caused by the bacteria Mycobacterium tuberculosis, which spread from an infected person through the air in respiratory droplets. In someone with a healthy immune system, TB can remain latent (inactive). It does not cause symptoms or spread or infect other people. If the immune system is impaired, however, as it is in HIV, TB can become active.

In active TB, the bacteria grow in the body and can spread through the lungs and other organs, including the brain and spine. A person with active TB can also transmit the infection to other immune-impaired people.

For these reasons, TB poses a serious health risk for people with HIV. Untreated, TB is one of the leading causes of death among people with HIV. 

You should be tested for tuberculosis (TB) if you are diagnosed with HIV. A number of effective treatments are available.

Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). Like HIV, HBV is a bloodborne virus that is transmitted via sexual contact with an infected person, or by sharing items (for example, needles for injection drug use) with an infected person that break the skin. It can also be transmitted to a newborn during delivery if the mother is infected. The shared routes of infection explain why many people who are at risk for HIV are also vulnerable to HBV infection.

HIV hastens the progression of liver disease in people coinfected with HBV, and it increases the risk of liver failure and liver-disease associated death. Coinfection also has an impact on strategies to manage HIV disease.

Hepatitis C virus (HCV) is also a liver infection that is transmitted via contact with the blood of someone who has HCV infection. In the U.S., HCV is most commonly spread when someone shares a needle or other equipment used to inject drugs. This is also one of the ways in which HIV is spread. Given the shared transmission routes, coinfection with HCV and HIV is common: Roughly a quarter of people with HIV are believed to be coinfected with HCV.

HCV is a major cause of chronic liver failure. HIV may cause chronic HCV to progress more rapidly. HCV infection can also complicate the treatment of HIV. 

Treating HIV Coinfections

Treatment of HIV and any coinfection is necessary. The presence of one coinfection can alter or complicate the treatment of the other. A physician with experience in treating HIV and coinfections may be best able to reduce medication interactions and optimize treatment.

In the case of TB/HIV coinfection, the timing of therapy and the medication regimens used depend on a number of factors and are tailored to address each patient’s health status. Treatment of TB focuses on preventing latent infection from developing into active, spreading disease, or on treating active TB infection.

Coinfection with HBC or HCV—or with both—puts you higher risk of developing liver failureand progression to liver cancer. You can also have an increased risk of death due to liver failure if these diseases are not treated.

A highly effective vaccine against HBV has been available for nearly four decades, but millions across the globe remain unvaccinated. Once HBV is acquired, treatments to control it are available, but they need to be taken for years. There is currently no cure.

HCV can now be treated with drugs that attack the virus. In most people, the disease is curable. Drug interactions are possible between HCV treatments and HIV medications, so doctors must be careful to prescribe the right combinations.

In addition, if a person is coinfected with HBV and HCV, the drugs used to treat HCV can cause the HBV infection to reactivate, illustrating how much coinfections can complicate treatments.

Coinfection vs. Secondary Infection

Coinfections aren't necessarily related to each other. A person may become infected with both at the same time or in separate incidents, but one disease doesn't make the other infection more likely.

By contrast, an infection that develops after or because of the original or primary infection is called a secondary infection. For example, a person with COVID-19 might develop a secondary bacterial pneumonia.

A primary infection has a few ways to increase susceptibility to secondary infection. For example:

  • It can impair immune function, giving other pathogens an opportunity to enter the body and cause infection. Altered immune function in primary infection with HIV, for example, makes it much easier for secondary infections, such as pneumonia, herpes simplex and herpes zoster, and candidiasis, to develop.
  • Its treatment can lead to a secondary infection. For example, antibiotic therapy for an infection can alter normal vaginal flora, leading to vaginal yeast overgrowth.
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  2. Centers for Disease Control and Prevention. Lyme disease: Transmission. Updated January 29, 2020.

  3. Lymedisease.org. About Lyme disease coinfections.

  4. National Institutes of Health. HIV and opportunistic infections, coinfections, and conditions. Updated September 24, 2020.

  5. Centers For Disease Control And Prevention. TB & HIV coinfection. Updated March 15, 2016.

  6. Singh KP, Crane M, Audsley J, Lewin SR. HIV-Hepatitis B virus co-infection: Epidemiology, pathogenesis and treatment. AIDS. 2017;31(15):2035-2052.

  7. National Institutes of Health. HIV and opportunistic infections, coinfections, and conditions. Updated September 24, 2020.

  8. Centers For Disease Control And Prevention. People coinfected with HIV and viral hepatitis. Updated September 21, 2020.

  9. National Institutes of Health. NIH strategic plan details pathway to achieving hepatitis B cure. Updated December 19, 2019.

  10. National Institute of Diabetes and Digestive and Kidney Diseases. Hepatitis C. Updated March 2020.

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