Diagnosis and tests for MERS
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 Influenza 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. Serological tests are no longer offered by the NIPH, but samples can be sent to the Public Health Agency in Sweden by agreement.
Who should be tested for the MERS virus?
There are currently few patients who have been tested for the MERS virus in Norway. So far, all tests have been negative. The Norwegian Institute of Public Health recommends that WHO's case definitions be used when assessing whether people should be tested for the MERS virus. In addition to acute respiratory tract infections among people who may have been exposed to the MERS virus, special attention should be paid to acute respiratory tract infections among healthcare workers treating patients with severe respiratory tract infections in hospitals and clusters of severe acute respiratory disease. Screening of healthy people returning from the Middle East or other areas with outbreaks is not recommended.
The following people should be tested for MERS and monitored:
- Persons with acute respiratory tract infection, clinically or radiologically confirmed *, where hospitalisation is required. Attention should be paid to atypical presentations in immunocompromised patients.
AND, in addition meets one or more of the criteria below:
- The person has within 14 days before the onset of symptoms stayed in the Middle East or other regions with recent outbreaks, unless another etiological agent can explain the clinical course.
- The disease is part of a cluster ** that occurs within a period of 14 days, regardless of travel history, unless another etiological agent can explain the clinical course.
- The disease occurs among healthcare professionals who treat patients with severe, acute respiratory infections. This applies in particular to patients in intensive care, regardless of travel history, unless another etiological agent can explain the clinical course.
- The clinical course is abnormal or unexpected; especially in case of rapid deterioration despite adequate treatment, and regardless of travel history and regardless of whether other etiology has been detected.
- People with acute respiratory tract infection, who for the last 14 days before the onset of symptoms have been in close contact *** with patients who have been diagnosed with the MERS virus or who have probably been infected with the virus while the disease was still ongoing.
- People with respiratory symptoms who have been to a health institution in the last 14 days in countries where MERS outbreaks have been reported in hospitals
- People with respiratory symptoms who have been in contact with camels / dromedaries in the last 14 days in countries where MERS is in circulation in the animal population, or where MERS has recently been detected in humans after infection from animals
* The medical history may include fever, cough and indications of parenchymal lung disease (e.g. pneumonia or acute pulmonary failure syndrome), and the diagnosis is based on clinical or radiological findings indicating consolidation.
** "Cluster" means two or more patients who have developed symptoms of acute respiratory infection within the same 14-day period, and who have had close contact with each other while the disease was ongoing, for example at work or school.
*** "Close contact" means
- People (family or health personnel) who have cared for the patient or in some other way have had similar close physical contact
- Household members or people who have visited the household.
It is not necessary to wait for other test results before testing for MERS.
Laboratory tests 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 in virus transport medium, can be pooled in same tube) and lower respiratory airways (bronchial wash). Faeces/urine are also a relevant sample for direct virus detection, but testing of respiratory samples and serum should take priority.
Serum samples can be taken for serological diagnosis during the first 10-12 days after symptoms start.
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 for close contacts to detect the virus.
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 before. 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.
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 not contagious when there is clinical improvement accompanied by two negative PCR tests from the respiratory tract and serum, with at least a day in between.