Released by WHO Nov 19th, 2013
# 7990
We’ve a detailed set of guidelines –published yesterday (Nov 19th) by the World Health Organization – that outlines the steps recommended for health officials to take when investigating contacts of known or suspected MERS cases.
While designed primarily as a reference text for public health officials doing contact investigation, this 24-page PDF file also provides us a much better idea of what is (or at least, should be) involved in these types of investigations.
Some highlights follow, but you’ll want to download and read the entire document. After which, I’ll return with a little more.
(Selected Excerpts)
1.1 OBJECTIVES
The data collected from this study will be used to characterize the key epidemiological transmission features of MERS-CoV virus, to help understand spread, severity, spectrum of disease, and impact on the community and to inform operational models for implementation of countermeasures such as case isolation, contact tracing and quarantine.
The primary objectives of this study are to:
- Estimate frequency of MERS-CoV infections (as measured by virologic and serologic tests) in
relation to human and other exposures (i.e. evaluate determinants/risk factors [including
sources] for infection) among contacts of confirmed MERS-CoV cases- Evaluate (modifiable) risk factors (e.g. exposures, behaviours, practices) for human MERS-
CoV infection- Evaluate the extent of MERS-CoV transmission among contacts of confirmed and probable
MERS-CoV patients- Describe the presentation and clinical course of disease with MERS-CoV infection
- Quantify the proportion of asymptomatic/sub-clinical MERS-CoV infections
COMMENT: Comprehensive study investigations such as the one described below can provide rich data to assess a number of secondary outcomes. Many other secondary objectives can be investigated in terms of epidemiological, immunological, clinical, virological, economic, genetic, behavioural, environmental, and animal factors associated with risk of MERS-CoV infection or outcome of infection. These are not discussed in detail in this protocol.<SNIP>
2.3.2 CONTACTS OF A CONFIRMED HUMAN MERS-COV CASE
The first stage of this investigation will be to identify all contacts of confirmed and probable MERS-CoV patients.
For the purposes of this study, contacts of a confirmed or probable human MERS-CoV case are defined as all individuals who are associated with some sphere of activity of the case and who may have similar environmental or other exposures as the case. Contacts can include household members, other family contacts, visitors, neighbours, colleagues, teachers, classmates, co-workers, servants, members of a social group, or others, and do not have to have had close personal contact with the case. Each group of contacts will form a separate, though sometimes overlapping, cohort of contacts. For example, one cohort may include all of the schoolmates who sit in the same classroom as the case if the case is a student, or office colleague of an office worker, even if they have not had recent close contact with the case. Alternatively, if the case owns a farm, or works on a farm, all of the workers on that farm could be included as contacts regardless of whether or not they had close physical contact with the case. The goal is to include a broad range of people with different types of exposures who have been part of the same environments as the case in order to be able to link type of exposure to evidence of infection.<SNIP>
2.4.3 DATA COLLECTION
After enrolment and informed consent, a standardized baseline data set will be collected with any specimens for MERS-CoV testing (and date of specimen collection). Baseline data to be collected include: age, gender, location, relationship to confirmed case-patient, occupation, signs and symptoms, and underlying conditions. In addition, detailed questions will be asked to evaluate risk factors for human infection with MERS-CoV (Appendix B). These are included in the data collection form in Appendix B under the section for “exposures” and include specific aspects of timing, frequency and duration of exposure(s). The questionnaire should be administered each time sera are collected. The study questionnaire for the use of all cases and contacts can be found in Appendix B.
2.4.4 PREVENTION OF MERS-COV TRANSMI SSION IN FRONT-LINE STAFF
Before study implementation, front-line staff, including all study personnel, will be trained in infection control procedures (standard, contact, droplet or airborne precautions), including proper hand hygiene and the correct use of surgical or respiratory face masks, if necessary, not only to minimize their own risk of infection when in close contact with patients during home visits and elsewhere, but also to minimize the risk of staff becoming a vector of MERS-CoV transmission between subjects or households.<SNIP>
2.5.2.1 VIROLOGIC TESTING
MERS-CoV case definitions are described above and can be found at:
http://www.who.int/csr/disease/coronavirus_infections/case_definition/en/index.html
As of 6 June, to consider a case as laboratory-confirmed, one of the following conditions must be met:
- positive RT-PCR or other validated molecular assays for at least two different specific targets
on the MERS-CoV genome
OR- one positive RT-PCR assay for a specific target on the MERS-CoV genome and an additional
different PCR product sequenced, confirming identity to known sequences of the new virus.A positive PCR assay for a single specific target without further testing is considered presumptive evidence of MERS-CoV infection. Final classification of cases will depend on clinical and epidemiological information, combined with laboratory data. Member States are requested to immediately notify WHO of any confirmed or probable case.
Full details for virologic laboratory testing of MERS-CoV can be found here:
http://www.who.int/csr/disease/coronavirus_infections/LaboratoryTestingNovelCoronavirus_21Dec12.pdf.<SNIP>
3.0 STUDY ENDPOINTS AND STATISTICAL ANALYSES
The following section discusses the endpoints – that is, what will be measured and calculated using the data that are collected in this study – for the primary objectives, including statistical advice.
3.1 STUDY OUTCOME MEASURES
3.1.1 PRIMARY OUTCOMES
The following will be assessed as study endpoints corresponding to the study’s primary objectives:
- Evaluate source(s), risk exposures, and (modifiable) risk factors for human infection with MERS-CoV
- Estimate the age-specific frequency of MERS-CoV infection (as measured by virologic and serologic tests) in relation to human and other exposures
- Describe the full spectrum of clinical disease associated with MERS-CoV infection
- Quantify proportion of asymptomatic/sub-clinical; mild illness; and severe illness(hospitalization/ICU/death) with MERS-CoV infection.
There is much more in this document, including a contract tracking line list and a multi-page questionnaire for contacts of MERS cases that asks about everything from living arrangements to previous medical history and habits (smoking & alcohol consumption), to recent travel history, to contact with animals in an attempt to gather the clearest possible picture of the risk factors involved in contracting this virus.
With cases and contacts being tested across multiple countries or regions it becomes increasingly important to standardize the methods by which they are investigated. As you might expect, standardized protocols make the comparison and collation of data far easier.
While it doesn’t always get as much attention as the high-tech work being done with molecular virology, it is often good old fashioned shoe-leather epidemiology – the tracking down of contacts, the gathering of extensive histories, and the laborious compiling and analysis of epidemiological line lists – that ends up telling us the most about how an outbreak is spreading.
