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Treatment and the treatment process

Antiviral medicines

During leukemia treatment, some viruses — especially those "sleeping" in the body — can become active again. Antiviral medicines prevent this and treat viral infections.

Last updated: ~2 min read
Small virus particles resting quietly along a glowing nerve fibre under a teal protective glow on a dark navy background.
Figure 1.Prevention stops viruses sleeping in the nerves from waking up.

01Short answer

Many people meet the herpes simplex virus (cold sores) and the chickenpox virus (VZV) in childhood; these viruses stay "asleep" in nerve cells for life. When immunity is weakened they can reactivate — causing mouth sores or shingles (herpes zoster). So in acute leukemia treatment, after transplant, and with fludarabine, alemtuzumab and some other drugs, preventive aciclovir or valaciclovir is often given. After transplant, cytomegalovirus (CMV) is monitored regularly in the blood by PCR and, if needed, letermovir (prevention), valganciclovir, ganciclovir or foscarnet are used. In hepatitis B carriers, entecavir or tenofovir prevent reactivation. For flu and COVID-19, specific antivirals help when started early.

02Simple explanation

Sleeping viruses. Some viruses stay silent in the body for years.

Waking up. When immunity is weak, they can reactivate.

Protection. Preventive tablets stop this.

Treatment. If a viral infection occurs, specific medicines are given.

03Scientific explanation

Herpes and VZV: aciclovir and valaciclovir block viral DNA polymerase; prophylaxis is standard for HSV-seropositive people during AML induction and allogeneic transplant (NCCN, ECIL).

CMV: after allogeneic transplant, letermovir prophylaxis in CMV-seropositive recipients reduces clinical CMV infection; otherwise a "pre-emptive" approach is used — treating when CMV DNA rises in the blood. Ganciclovir and valganciclovir can suppress the marrow.

Hepatitis B: in HBsAg-positive or anti-HBc-positive people, anti-CD20 antibodies and transplant raise the risk of reactivation; entecavir or tenofovir prophylaxis continues throughout treatment and for a while afterwards. Oseltamivir is used for flu and nirmatrelvir–ritonavir or remdesivir for COVID-19; ritonavir interacts with many leukemia drugs.

04What happens in the body?

Why prevention?

With weak immunity, shingles and herpes can be more severe. One tablet a day greatly lowers this risk. Your doctor will say how long to continue it.

How do they work?

To copy itself, a virus uses a special enzyme inside the cell. An antiviral blocks this enzyme so the virus cannot multiply. These medicines do not remove the virus completely; they keep it under control.

A virus’s copying chain of light on a dark background is stopped by a small golden block.
Figure 2.An antiviral stops the virus from multiplying.

Monitoring

After transplant, CMV and sometimes other viruses (EBV, adenovirus) are checked regularly in the blood. This allows treatment to start before symptoms appear.

A modern PCR instrument with a small tray of blood samples in teal light.
Figure 3.After transplant, viruses are monitored in the blood.

05Protecting against viruses

A simplified outline.

Testing — Hepatitis, HIV, herpes.1TestingHepatitis, HIV, herpes.
Prevention — A daily tablet.2PreventionA daily tablet.
Monitoring — CMV PCR.3MonitoringCMV PCR.
Treatment — When needed.4TreatmentWhen needed.
Preventing reactivationHerpes, shingles, hepatitis.
Early detectionVirus in the blood.
InteractionsChecked by the doctor.

06Antiviral medicines in leukemia

VirusMedicinePurpose
Herpes simplex, VZVAciclovir, valaciclovirPrevention and treatment
CMVLetermovirPrevention after transplant
CMVValganciclovir, ganciclovir, foscarnetTreatment
Hepatitis BEntecavir, tenofovirPreventing reactivation
FluOseltamivirEarly treatment
COVID-19Nirmatrelvir–ritonavir, remdesivirEarly treatment; interactions!

* Your doctor decides the medicine, duration and availability.

07Key terms

Reactivation
A sleeping virus becoming active again.
VZV
The chickenpox and shingles virus.
CMV
Cytomegalovirus.
Prophylaxis
Preventing infection.
Pre-emptive treatment
Treating a rising virus before symptoms appear.
PCR
A test that detects a virus’s genetic material.

08Key points

  • Sleeping viruses can wake when immunity is weak.
  • Preventive tablets stop this.
  • Hepatitis is tested before treatment.
  • CMV is monitored after transplant.
  • Early treatment helps with flu and COVID-19.
  • Check interactions with your doctor.

09Frequently asked questions

How long does aciclovir prevention last?

It depends on the treatment — sometimes throughout treatment, and often a year or more after transplant.

Can I have a shingles vaccine?

The recombinant (non-live) shingles vaccine is recommended for some people; talk to your doctor.

Someone in my family has flu — what should I do?

Tell your team; a preventive medicine may sometimes be offered.

Do antivirals affect the kidneys?

Some do; so kidney tests are monitored and drinking plenty is advised.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. How long does aciclovir prevention last?

  2. Can I have a shingles vaccine?

  3. Someone in my family has flu — what should I do?

  4. Do antivirals affect the kidneys?

My questions

12Sources

  1. National Cancer Institute (NCI). Chemotherapy to Treat Cancer
  2. Cancer Research UK. Chemotherapy
  3. National Cancer Institute (NCI). Infection and Neutropenia during Cancer Treatment
  4. MedlinePlus. Aciclovir (acyclovir)
  5. Centers for Disease Control and Prevention (CDC). Preventing Infections in Cancer Patients
  6. NHS. Shingles
  7. NHS. Acute kidney injury
  8. MedlinePlus. Therapeutic drug levels
  9. Canadian Cancer Society. Liver problems
  10. MedlinePlus. Bilirubin Blood Test
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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