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  • Diagnosis and tests for MERS


Diagnosis and tests for MERS

Here is an overview of who should be tested for MERS-CoV and how it should be done.

Reagensrør i laboratorieomgivelser
Illustrasjonsfoto: Colourbox.com

Here is an overview of who should be tested for MERS-CoV and how it should be done.

Samples should be tested where there is suspicion of MERS-CoV. The recommended method is PCR.

The Department of Influensa at the Norwegian Institute of Public Health (NIPH) has diagnostic tests for MERS-CoV and can receive samples from hospitalised patients for confirmation. The Department of Microbiology at St. Olav's Hospital in Trondheim can also perform diagnostic tests but serological tests are only done at the NIPH. 

Laboratory test for MERS

Two sets of respiratory samples and a serum test for MERS

Take samples from the upper and particularly the lower respiratory tract. Diagnostic experience with the first disease cases showed that virus detection is most successful with material from the lower respiratory tract. 

When the sample is taken, the NIPH recommends that two sets of respiratory specimens (one for local testing and one to be sent to NIPH), from upper respiratory airways (nasopharyngeal secretions AND throat secretions i virus transport medium, can be pooled in same tube) and lower respiratory airways (bronchial wash). Faeces are also a relevant sample for direct virus detection, but testing of respiratory samples should take priority.

Serum samples can be taken for serological diagnosis during the first 10-12 days after symptoms start. Serum samples for serological diagnosis requires both acute phase samples and samples taken after 14-21 days.

All three samples should be taken sequentially during the course of the disease if there is strong clinical suspicion. 

Follow the hospital's infectious disease control procedures when taking samples. Consult the hospital's infectious disease control physician or Duty Medical Officer at the NIPH for isolation measures / infectious disease control measures and sampling. One set of samples should be analysed locally for common respiratory agents while the other should be sent to the Department of Virology at the NIPH for specific PCR analysis for MERS-CoV.

With contact tracing around confirmed cases of MERS in Norway, asymptomatic close contacts will also be tested. Samples will be taken from upper respiratory airways, together with two serum samples; one set within 14 days  after the last contact with the MERS-patient, the other set 2-3 weeks later.

Possible co-infections

Positive tests for other infections do not rule out infection with MERS-CoV, as co-infection (especially influenza, streptococci, Haemophilus influenzae type B, legionella ) have been seen. Make arrangements in advance with the local microbiology laboratory and Department of Virology at the NIPH before shipment. 

When submitting the sample, include clinical information such as symptoms, their onset, date admitted to hospital, travel history and any underlying diseases in the notes. Mark clearly if MERS-CoV is suspected.

Transport of samples

Mix virus transport medium with the respiratory samples and transport under refrigeration at 4 °C (wet ice or cooling block that is not in direct contact with the sample). Label and pack the sample correctly. In practice it may be difficult for general practitioners and emergency rooms to send samples in a cooled state. In such cases, keep the sample cool until shipment. Transport should take place as quickly as possible to the local microbiology laboratory.

Repeat negative MERS tests?

Consider repeating respiratory tract tests if the first sample taken during the acute phase is negative, and there is still strong clinical suspicion. There have been reported cases where the initial test was negative and samples taken a few days later proved to be positive.

Positive test

With a confirmed MERS-diagnosis, the patient should be followed up with regular testing of samples from the upper and lower respiratory airways with PCR every second to fourth day as a minimum. Repeated samples of other types (e.g. serum, urine, faeces) should also be examined by PCR to better understand the replication kinetics of the virus and to help with infectious disease control around the patient.  The patient is considered to be uncontagious when there is clinical improvement accompanied by two negative PCR tests from the airways and serum, with at least a day in between.