Respiratory Viral Infections in Haem Malignancies and Transplant (2016)

 

Resp Virus Characteristics

 

Human Metapneumovirus – subtypes A&B – RNA virus negative sense – 5 days incubation

Respiratory Syncytial Virus – subtypes A&B – RNA virus negative sense – 4 days incubation

Parainfluenza – subtypes 1-4 - RNA virus negative sense – 2 days incubation

Influenza – subtypes A-C – RNA virus negative sense – 1 day incubation

 

Rhinovirus – species A-C – RNA positive sense – 2 days incubation

 

Diagnosis

 

URTI – detection of respiratory virus in samples taken above and including the larynx

URT disease – URTI plus signs or symptoms of infection

LRTI - detection of respiratory virus in samples taken below the larynx

LRT disease – LRTI plus hypoxia, pulmonary infiltrates or pathological sputum production.

 

Diagnostic test – quantitative nucleic acid amplification test (NAAT) – generically called PCR.

 

Risk factors for progression to RSV LRTI in allograft patients

-       Pre-engraftment

-       Lymphopenia (<0.2)

-       Older age

-       GVHD

-       Mismatched or unrelated donors

-       Neutropenia (<0.5)

 

Prevention

 

Vaccination

–      recommended for patients, household contacts and healthcare workers

 

Post-Exposure Prophylaxis for ‘Flu

-       If not vaccinated, become immunosuppressed since vaccination, HSCT, Rituximab

-       Recommendation updated annually

-       Currently oseltamavir 75mg daily for 10 days if the dominant ‘flu strain is lower risk for resistance, e.g. H3N2. Start within 48 hours of exposure.

 

Infection Control

-       Hand hygiene

-       PPE gloves gown mask

-       Safe disposal of secretions

-       Isolate Haem inpatients in neutral pressure side room (antechamber if available)

-       Isolate outpatients with symptoms where possible

-       Advise of relatives not visiting if symptomatic

 

Management

 

Supportive Care

-       Screen for co-pathogens, e.g. PCP

-       Early involvement of critical care if signs of respiratory failure

-       Reduce immunosuppression where possible

 

Postponing planned chemo / transplant

-       Symptomatic patients should be screened prior to starting treatment

-       Decision to delay treatment is patient-by-patient, depending whether pace/stage of disease allows

 

Influenza

-       Limited data but what is available shows reduced mortality and reduced progression to pneumonia with the use of antiviral therapy.

-       Neuroaminidase inhibitors (NAI) interfere with release of virus particles from infected cells and so prevent spread of infection.

-       1st line - Annual change in drug / dosing. Currently oseltamavir 75mg BD for 5 days, or zanamivir inhaler if dominant strain more likely to be oseltamivir resitant.

-       2nd line – zanamivir inhaler / nebulizer / intravenous if poor GI absorption or failure of first line treatment.

-       New investigational agents – favipiravir – inhibitor of viral RNA polymerase.

 

RSV

-       Treatment only indicated in allograft

-       Ribavirin

o   Neb / IV / oral

o   Problems with availability and licensing, and significant side effects. E.g. nebulizer teratogenic, IV causes haemolysis. Nebulised ribavirin does appear to reduce mortality and morbidity in small studies. Risk scoring system available to address who to treat.

o   Oral not licensed but small study data to show may be effective if nebulized not available or contraindicated.

-       IVIG can be given in combination with ribavirin if available.

 

Human Metapneumovirus

-       Treated of URTI not required

-       IVIG 0.4g/lg weekly has been used in small studies for LRTI cases

-       Ribavirin not routinely recommended but consider in very high risk infections

 

Parainfluenza

-       Supportive treatment

-       Ribavirin not routinely recommended but consider in very high risk infections

 

Rhinovorius

-       Supportive treatment