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Immunity and infection prevention

Viral infections

The main article (“Viral infections”) explains viruses in general. This topic looks more deeply at the viral infections that matter most in leukaemia: dormant viruses waking up, and respiratory viruses.

Last updated: ~1 min read
A quiet virus inside a cell nucleus.
Figure 1.A dormant virus can wake up.

01Short answer

Viral infections cause problems in two ways. First, viruses “sleeping” in the body (herpes simplex, varicella-zoster, cytomegalovirus (CMV), hepatitis B) can reactivate when immunity weakens. This is why some treatments (for example some antibodies and transplant) come with antiviral prevention or regular blood tests. Second, respiratory viruses such as flu, RSV and COVID-19 can progress to severe pneumonia when immunity is weak. Viruses are usually found with a PCR test. Vaccines, hand hygiene and keeping away from people who are ill are the basis of protection.

02Simple explanation

Dormant viruses can wake up.

Respiratory viruses can become severe.

PCR finds viruses.

03Scientific explanation

Reactivation: when T-cell function weakens, herpes viruses, CMV and hepatitis B can reactivate; hepatitis B is often tested before treatment.

Respiratory viruses: after a transplant, RSV and flu can spread from the upper airways to the lungs.

04What happens in the body?

A dormant virus

A virus can stay quiet for years and wake when immunity weakens.

Viruses in the air

Viruses spread by droplets are more dangerous when immunity is weak.

Small droplets in the air.
Figure 2.Viruses spread by droplets.

A PCR test

Viral genetic material is found in a nose swab or blood sample.

A swab and a PCR tube.
Figure 3.PCR finds the virus.

05How reactivation happens

Four steps.

Dormant — The virus hides.1DormantThe virus hides.
Weakening — Immunity falls.2WeakeningImmunity falls.
Waking — The virus becomes active.3WakingThe virus becomes active.
Control — Antivirals and monitoring.4ControlAntivirals and monitoring.

06Viruses that matter in leukaemia

VirusWhat can be done
Herpes simplex, zosterAntiviral prevention
CMVMonitoring with blood tests (especially after transplant)
Hepatitis BTesting before treatment, prevention if needed
Flu, RSV, COVID-19Vaccination, hygiene, seeking help early

07Key terms

Reactivation
A dormant virus becoming active again.
CMV
Cytomegalovirus.
Antiviral
A medicine against viruses.
PCR
A test that finds viral genetic material.
Zoster
Reawakened chickenpox virus (shingles).

08Key points

  • Viruses cause harm in two ways.
  • Dormant viruses can wake up.
  • Respiratory viruses can become severe.
  • PCR finds the virus.
  • Do not stop prevention.
  • Vaccines and hygiene protect you.

09Frequently asked questions

Why am I tested for hepatitis B?

Some treatments can wake up dormant hepatitis B; testing and prevention stop this.

How dangerous is shingles?

With weak immunity it can spread; show any rash at once.

What if my family is ill?

Keep your distance and use masks and hand hygiene (“Contacts, family and crowds”).

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. Why am I tested for hepatitis B?

  2. How dangerous is shingles?

  3. What if my family is ill?

My questions

12Sources

  1. MedlinePlus (U.S. National Library of Medicine). Viral Infections
  2. National Cancer Institute (NCI). Infection and Neutropenia during Cancer Treatment
  3. World Health Organization (WHO). Vaccines and immunization
  4. National Institute for Health and Care Excellence (NICE). Neutropenic sepsis: prevention and management in people with cancer (CG151)
  5. Clinical Infectious Diseases (IDSA), 2011. Clinical Practice Guideline for the Use of Antimicrobial Agents in Neutropenic Patients with Cancer: 2010 Update by the Infectious Diseases Society of America
  6. Annals of Oncology (ESMO), 2016. Management of febrile neutropaenia: ESMO Clinical Practice Guidelines
  7. Journal of Clinical Oncology (ASCO and IDSA), 2018. Outpatient Management of Fever and Neutropenia in Adults Treated for Malignancy: American Society of Clinical Oncology and Infectious Diseases Society of America Clinical Practice Guideline Update
  8. Journal of Clinical Oncology, 2000. The Multinational Association for Supportive Care in Cancer Risk Index: A Multinational Scoring System for Identifying Low-Risk Febrile Neutropenic Cancer Patients
  9. Centers for Disease Control and Prevention (CDC). Information for Patients Who Are Getting Chemotherapy
  10. American Cancer Society. Infections and Cancer
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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