Written and maintained by CASRAI Editorial Board
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General product and regulatory information for laboratory and clinic staff. It is not medical advice and does not describe how to collect a specimen. Follow the instructions for use supplied with a kit and the requirements of the receiving laboratory.
Short answer
Viral transport medium (VTM) is a transport medium sold for respiratory and other viral specimens. It is a device that keeps a specimen in a stable condition between collection and the laboratory. In the United States, FDA regulates most VTM types as Class I devices under 21 CFR 866.2390. The COVID-19 enforcement policy that once let some VTM be distributed without a marketing submission has ended.
What is a transport medium?
A transport medium holds a specimen between the collection site and the laboratory. The federal regulation for transport culture media (21 CFR 866.2390) describes the device as one that “maintains the viability of suspected pathogens contained in patient specimens while in transit from the specimen collection area to the laboratory” and classifies it as Class I (general controls). That wording comes from the regulation itself, which describes a semisolid, usually non-nutrient medium; viral media are regulated under the same regulation number.
Different media suit different specimens and organisms. A bacterial culture swab system and a viral swab system can look alike, but they are different products. For the bacterial side (Stuart, Amies and other media in a swab tube), see throat culture swab types and transport media and ESwab and its liquid Amies medium.
VTM, UTM and “VTM kit”: the terminology
Viral transport medium (VTM)
VTM is the common name for transport medium sold for viral specimens. In FDA’s product code list, the codes for these media sit under the same regulation number as bacterial transport media (see the table below).
Universal transport medium (UTM)
“Universal transport medium” appears in the literature as a named comparator. A 2014 paper in Diagnostic Microbiology and Infectious Disease compared a room-temperature molecular transport medium (PrimeStore) with UTM that was stored frozen and shipped on dry ice, using paired nasopharyngeal swabs from 233 Honduran children under 5. The two systems were similar for the four most common viruses, but for RSV the molecular medium detected 12 of 22 UTM-positive specimens (sensitivity 54.55%). The authors noted the small sample and that storage was not standardized. One study does not rank products; it shows that “transport medium” is a category in which media can behave differently for different viruses. For general information on the shipping coolant, see what dry ice is.
What is a UTM swab?
A “UTM swab” or “viral transport medium swab” is the shorthand for a collection swab supplied together with a tube of transport medium, so that the swab goes into the medium after collection. The name describes a pairing of a swab and a medium, not a single standard product; the exact swab material, medium and tube vary by kit and manufacturer. Whether a given kit is suitable for a given test is set by the test’s own instructions and the laboratory that runs it.
What is Cary-Blair transport medium used for?
Cary-Blair is a bacterial transport medium, not a viral one. In BD’s published range, as summarised in the CASRAI throat culture swab guide, Cary-Blair is the option listed for faecal specimens.
How can viral chlamydia or mycoplasma cultures be transported?
Chlamydia and mycoplasma are bacteria, so “viral chlamydia” is a mixed-up phrase; the question usually means a transport system for chlamydial or mycoplasma specimens. The answer depends on the test and the receiving laboratory: the laboratory’s specimen requirements, or the instructions for use of the kit it supplies, state the medium, temperature and time limit. A medium cleared for one use is not automatically suitable for another. Organism-specific media are not covered here.
FDA classification and product codes
FDA’s page “FAQs on Viral Transport Media During COVID-19” (dated Aug 11, 2026) states that FDA “is not continuing the enforcement policy described in the COVID-19 Transport Media Policy”. FDA may refrain from objecting to continued distribution of some devices only if a marketing submission was accepted by Nov 7, 2023 and FDA had not taken final action. It places most VTM types under 21 CFR 866.2390, PBS or saline transport media generally under 21 CFR 866.2300 (generally exempt from 510(k), but registration, listing and labeling still apply) and certain inactivating transport media under 21 CFR 866.2950. Cleared VTM devices can be found under product code JSM in FDA’s 510(k) database.
| Product code | Name in FDA’s classification database | Class | Regulation |
|---|---|---|---|
| JSM | Culture Media, Non-Propagating Transport | 1 | 21 CFR 866.2390 |
| JSN | Culture Media, Propagating Transport | 1 | 21 CFR 866.2390 |
| QMC | Transport Medium, Notified Per The Vtm Guidance | 1 | 21 CFR 866.2390 |
| JTW | System, Transport, Aerobic | 1 | 21 CFR 866.2900 |
| JTX | Transport Systems, Anaerobic | 1 | 21 CFR 866.2900 |
Source: openFDA device classification API (checked 2026-11-01). The QMC definition reads “Notified transport media and collection devices intended for specimen collection and transport for use in detection of respiratory viruses including coronavirus per the guidance.”
Where it matters for labs and clinics
During the 2020 shortage, CDC posted a standard operating procedure (SOP) so that laboratories could prepare their own VTM, in a Laboratory Outreach Communication System alert dated 03/21/2020 addressed to clinical laboratory professionals. That was an emergency measure. FDA’s current FAQ says the related enforcement policy is no longer continued, so a purchasing or quality decision should rest on the device’s current regulatory status rather than on 2020 shortage-era arrangements. FDA recommends contacting the agency, or using a Q-Submission, for questions about a specific device.
Common misunderstandings
- “VTM and UTM are interchangeable with any bacterial transport swab.” No. Bacterial culture systems such as Stuart, Amies and Cary-Blair are a different product group; see the agar plate guide for how culture media differ from transport media.
- “The COVID-19 transport media policy still applies.” FDA states it is not continuing it.
- “One study shows which medium is best.” The 2014 comparison covers two systems, one population and one storage setup, and reports a virus-specific difference for RSV only.
FAQ
What is a transport medium?
A device that keeps suspected pathogens viable in a patient specimen while it travels from the collection site to the laboratory (21 CFR 866.2390, Class I).
What is a UTM swab?
A collection swab supplied with a tube of universal or viral transport medium. The name describes the pairing; contents and suitability depend on the kit and on the test the laboratory runs.
What is Cary-Blair transport medium used for?
It is a bacterial transport medium; BD lists it for faecal specimens.
How can viral chlamydia or mycoplasma cultures be transported?
The receiving laboratory or the kit’s instructions for use set the medium, temperature and time limit; this page does not give a protocol.
Is viral transport medium regulated by FDA?
Yes. Most VTM types fall under 21 CFR 866.2390 as Class I devices, and FDA ended the COVID-19 transport media enforcement policy.
Sources
All sources below were checked on 2026-11-01.
- FDA, “FAQs on Viral Transport Media During COVID-19” (page dated Aug 11, 2026): https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/faqs-viral-transport-media-during-covid-19
- openFDA device classification API: https://api.fda.gov/device/classification.json
- 21 CFR 866.2390, Transport culture medium: https://www.law.cornell.edu/cfr/text/21/866.2390
- CDC Laboratory Outreach Communication System, lab alert of 03/21/2020 on a new SOP for creating VTM: https://www.cdc.gov/locs/dynamic-temp/2020/new_sop_for_creating_vtm.html
- Diagn Microbiol Infect Dis 2014;80(2):107-110, “Comparison of a new transport medium with universal transport medium at a tropical field site”: https://pmc.ncbi.nlm.nih.gov/articles/PMC4164576
