Viral Haemorrhagic Fevers – Including Ebola Disease

Testing Indications

A clinical risk assessment is required prior to requesting VHF testing. This should include a review of the clinical status, travel and exposure history and consideration of alternative differential diagnoses for all individuals suspected of a VHF infection. Additional discussion via a coordination call with other testing partners, stakeholders, and ministry may be required.

VHF infection should be initially 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)

Other more common and potentially fatal infectious diseases including malaria, typhoid fever, and bacteremia should be considered in the differential diagnosis of individuals with a VHF-compatible clinical illness. Consult your usual microbiology laboratory service if routine microbiological testing for non-VHF pathogens is required (e.g. blood cultures). Malaria testing can be performed at PHO in parallel with testing for VHF agents, where applicable.

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 receiving approval by the PHO Microbiologist 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 Viral Hemorrhagic Fevers including Ebola Virus Disease for additional information on when repeat testing and specimen collection may be considered. 

Storage and Transport

The collection, transport and handling of specimens from patients suspected of VHF requires strict adherence to federal 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 Specimens Requiring Emergency Response Assistance Plan (ERAP) For Transport within Canada for information on the process associated with collection and 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 upon receipt of a specimen at PHO (STAT). The TAT for PHO testing during a specific response will be determined at the time of submission.

Confirmatory PCR testing will be performed at the NML regardless of PHO’s preliminary results. PHO will forward the specimen onto the NML for testing. 

PHO screens for VHF-causing viruses by PCR using protocols developed at the NML. Each PCR assay is designed to detect 2 gene targets per virus except for the Sudan virus where only 1 viral gene target is detected.

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 that have been approved after a discussion between the PHO Microbiologist and the requesting healthcare provider(s). Each VHF test requires a separate order to be indicated on the General Test Requisition.

In accordance with federal guidelines, PHO screening results require confirmation by PCR testing at the NML. Depending on the prevalence of a particular virus at the time of testing and the clinical features of the individual case, negative test results may be reported as final by PHO, or may be re-tested at the NML for final reporting.

Interpretation

All results should be interpreted in the context of the clinical history and other pathological findings.

VHF PCR Result:

Not Detected:
Nucleic acids from the virus tested were not detected in the specimen. This does not exclude infection. Confirmatory testing will be performed at the NML.

Notes:

• Submit a second specimen >72 hours after symptom onset only if the first specimen was negative and collected <72 hours after symptom onset AND if a VHF is still suspected on reassessment of the patient (e.g. no clinical improvement >72 hours after symptom onset).
• No additional testing is required if a negative result is obtained on a specimen 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 a number of reasons (e.g. only a single viral target was detected, inhibitory substances were detected, among others). Confirmatory testing will be performed at 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. Confirmatory testing will be performed at the NML.

Notes:

Reporting

The reporting plan will be communicated to stakeholders at the time of testing. The report issued by PHO for any VHF testing is considered preliminary and requires confirmation by the NML.

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