Viral Hemorrhagic Fevers (VHFs)

Testing Indications

A clinical risk assessment is necessary to support all VHF test requests. Information on the individual’s signs/symptoms, travel and exposure history and consideration of alternative differential diagnoses will be required for testing-related discussions with PHO’s microbiologist.

A VHF should be suspected if, within 21 days (3 weeks) prior to illness onset, the individual has developed fever and has a:

• Clinical illness compatible with a VHF infection
  AND
• Relevant travel history (e.g. travel to any geographic area with active VHF outbreaks OR any country where sporadic VHF cases occur)
  AND/OR
• Relevant epidemiological exposure (e.g. contact with confirmed positive case)

Refer to PHO’s Viral Hemorrhagic Fever (VHF) Symptom and Exposure Risk Assessment for Clinician Use for more information.

Acceptance/Rejection Criteria

Specimens will not be tested without prior notification and consultation with a PHO Microbiologist.

Timing of Specimen Collection

• Collect specimens as soon as possible after a PHO Microbiologist has agreed to testing and following a discussion with the relevant testing partners, stakeholders and ministry.
• Specimens collected at least 72 hours from the onset of symptoms are preferred due to variability in viral load during the early stages of infection.  
• Refer to Laboratory Guidance Diagnostic Testing for Viruses That Cause Hemorrhagic Fevers for additional information on when repeat testing and specimen collection may be considered.

Storage and Transport

The transport and handling of specimens from patients suspected of VHF requires adherence to federal shipping and transportation regulations, including the activation of an Emergency Response Assistance Plan (ERAP). All clinical specimens must be shipped in accordance with the Transportation of Dangerous Goods Act.

Please refer to Laboratory Guidance Diagnostic Testing for High-Risk Viral Pathogens That Cause Hemorrhagic Fevers, Including Ebola Disease, for information on the process associated with transport of specimens from patients with a suspect VHF. Additional information will be provided at the time of the request.

Specimens should be stored at 2-8°C following collection and shipped to PHO on ice packs according to the ERAP procedure.

Test Frequency and Turnaround Time (TAT)

Testing for the VHF-causing viruses listed above is performed only upon request.

Tests will be performed as soon as possible once specimens have been received at PHO.

The TAT for PHO testing during a specific response (and confirmatory testing at the NML) will be determined at the time of submission.

PHO detects the nucleic acids of VHF-causing viruses by RT-PCR using protocols developed at the NML.

A single EDTA blood specimen can be used to test for multiple VHF-causing viruses, however, the PCR for each virus is performed as a separate, independent test i.e. it is not a single multiplex reaction.

Algorithm

PHO will only test for the specific VHF-causing viruses agreed to after a discussion between a PHO Microbiologist and the requesting healthcare provider(s).

Results of PHO RT-PCR tests will be confirmed by the NML.

Interpretation

All results should be interpreted in the context of the clinical history and other pathological findings. Refer to the Laboratory Guidance Diagnostic Testing for Viruses That Cause Hemorrhagic Fevers .

VHF PCR Result:

Not Detected:
Nucleic acids from the virus tested were not detected in the specimen. This does not exclude infection. Result will be confirmed by the NML.

Notes:

• Submit a second specimen >72 hours after symptom onset only if viral nucleic acids were not detected in the first specimen and was collected <72 hours after symptom onset AND if there is still a high suspicion of a VHF on reassessment of the patient (e.g. no clinical improvement >72 hours after symptom onset).
• No additional VHF testing at PHO is required if the specimen was collected >72 hours after symptom onset. Other testing appropriate for patient care can proceed.

Indeterminate:
It is unclear if nucleic acids from the virus of interest are present in the specimen. This does not exclude infection and can arise for several reasons (e.g. only a single viral target was detected, inhibitory substances were detected, among others). Result will be confirmed by the NML.

Detected:
Nucleic acids from the virus of interest were detected in the specimen. This may indicate that the individual has an acute infection. Result will be confirmed by the NML.

Reporting

The reporting plan will be communicated to stakeholders at the time of testing.

Results are reported to the ordering physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

Test results are also reported to the Medical Officer of Health as per Health Protection and Promotion Act.

References

1. De La Vega M-A, Caleo G, Audet J, Qiu X, Kozak RA, Brooks JI, et al. Ebola viral load at diagnosis associates with patient outcome and outbreak evolution. J Clin Invest [Internet]. 2015 [cited 2024 Jul 3];125(12):4421–8. Available from: https://pubmed.ncbi.nlm.nih.gov/26551677/
2. Grolla A. Real-time and end-point PCR diagnostics for Ebola virus. In: Ebolaviruses. New York, NY: Springer New York; 2017. p. 341–52.
3. Nikisins S, Rieger T, Patel P, Müller R, Günther S, Niedrig M. International external quality assessment study for molecular detection of Lassa virus. PLoS Negl Trop . 2015;9(5):e0003793. Available from: http://dx.doi.org/10.1371/journal.pntd.0003793
4. Nsio J, Kapetshi J, Makiala S, Raymond F, Tshapenda G, Boucher N, et al. 2017 outbreak of Ebola virus disease in northern democratic republic of Congo. J Infect Dis. 2019 [cited 2024 Jul 3];221(5). Available from: https://pubmed.ncbi.nlm.nih.gov/30942884/
5. Pang Z, Li A, Li J, Qu J, He C, Zhang S, et al. Comprehensive multiplex one-step real-time TaqMan qRT-PCR assays for detection and quantification of hemorrhagic fever viruses. PLoS One. 2014;9(4):e95635. Available from: http://dx.doi.org/10.1371/journal.pone.0095635
6. Laboratory Guidance Diagnostic Testing for Viruses That Cause Hemorrhagic Fevers