The accuracy of a medical diagnosis begins with two key components: the right tool for collecting an ample amount of a viral sample and careful storage of that material as it is transferred to a laboratory for analysis. Viral samples can rapidly decay if not stored appropriately during transport. This is why it’s vital to select the right viral transport media.
Below we’ll define viral transport media and when it is used, explain the typical components and options, as well as the average price range for viral transport media.
What is viral transport media?
A viral transport medium (or media, plural) is a solution that allows for the safe transfer of viral samples to a laboratory for analysis. In many cases, this is a liquid that provides a balanced buffer solution for maintaining a neutral pH, antimicrobial agents, a source of protein, and sucrose that serves as a preservative.
Without ultra-low temperature storage or appropriate viral transport media, many viral specimens will begin to degrade rapidly. This increases the risk of a false-negative result during analysis at the laboratory.
What makes viral transport media effective?
The effectiveness of viral transport media lies in its ability to preserve the integrity of the viral sample during transit. Factors that contribute to this include:
pH balance
A balanced buffer solution maintains a neutral pH, protecting the viral RNA or DNA from degradation.
Antimicrobial properties
Many transport media include antimicrobial agents to prevent contamination by bacteria or fungi.
Preservation techniques
Ingredients like sucrose act as preservatives, extending the viability of viral samples.
Temperature Stability
High-quality media can stabilize viral specimens across a range of temperatures, ensuring usability even under varying transport conditions.
How Does Viral Transport Medium Work?
At its core, a viral transport medium is a carefully balanced solution engineered to protect and preserve clinical specimens during the critical window between sample collection and laboratory analysis. But how does it actually do that?
Puritan’s UniTranz-RT® universal transport medium uses a modified Hank’s Balanced Salt Solution fortified with stabilizers and antimicrobial agents that work together to ensure sample viability. Here’s a closer look at the key components and their functions:
- Buffer Salts and HEPES: These maintain a neutral pH (7.3 ± 0.2), critical for preserving the integrity of sensitive viruses and bacteria during transit.
- Gelatin and Bovine Serum Albumin: These act as protein sources and stabilizers, especially important for supporting the viability of fastidious organisms such as Mycoplasma and Chlamydia species.
- Sucrose and Glutamic Acid: These provide cryoprotection and nutrient preservation, aiding in sample stability even during freezing or extended storage.
- Antimicrobial Agents: A combination of Amphotericin B, Vancomycin, Colistin, and L-Cysteine inhibits bacterial and fungal contaminants that could otherwise compromise the sample.
- Phenol Red: A pH indicator that helps end users identify potential contamination or degradation (e.g., a color change from pink to yellow).
Together, these components create a viral transport medium that supports broad pathogen compatibility, including viruses, chlamydiae, mycoplasmas, and ureaplasmas, while enabling reliable diagnostic outcomes even under room temperature storage conditions.
Pro Tip: Puritan’s UniTranz-RT® medium is validated for up to 48 hours of specimen stability at 4°C or 20–25°C, making it ideal for clinical environments with varying transport logistics.
Viral Transport Medium Trends
With advancements in diagnostics and increasing global testing demands, the field of viral transport media is evolving. There is a growing emphasis on precision and efficiency in viral diagnostics.
Two recent trends include:
1. Compatibility with molecular diagnostics
As PCR and other molecular testing methods dominate, media optimized for DNA/RNA preservation are gaining popularity.
2. Customizable solutions
Manufacturers are increasingly offering customizable kits tailored to specific viruses or testing methods.
What are the components of viral transport medium?
A viral transport system depends upon more than the viral transport media solution. The value of the transport is that the DNA of the microbe can be recovered after the specimen is no longer viable for culturing.
1. Viral transport tube
Viral transport media is included in a sterile tube typically made of premium medical grade plastic. Some tubes may be formulated to contain buffered proteins and antibiotics that suppress the growth of potentially contaminating bacteria and fungi.
2. Viral transport cap
A securely closed transport tube is critical for protecting the sample specimen from contamination during transport. Many tubes feature screw caps designed for secure closure and ease of use, while other transport tubes may feature a plug top for a secure seal.
3. Collection swab
Some viral transport media and transport systems are formulated to work with a specific type of swab. Not all swab materials are suitable for viral specimen collection. For example, nasopharyngeal swabs cannot be made with cotton as organic materials interfere with the polymerase chain reaction (PCR) testing process. Some manufacturers sell swab kits that include viral transport systems, to eliminate any confusion around the right components.
Crafting perfection for your requirements - Puritan Medical Products offers premier custom swab manufacturing services. Elevate your medical devices with precision engineering.
Common viral transport media uses
Viral transport media is used for the preservation of a wide range of viral specimens, including infections that are difficult to diagnose on the spot and instances where knowing a specific viral strain can support diagnosis or public health efforts. Common viral transport media uses include:
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Influenza virus: Universal viral transport media help maintain viral respiratory swab sample viability at room temperature up to 48 hours, allowing for health experts to diagnose specific strains of influenza.
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SARS-CoV-2: According to the FDA not all transport media are compatible with SARS-CoV-2 testing platforms. It is important to select viral transport media cited for use in coronavirus testing or approved for this use by the FDA.
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Enterovirus D68: This non-polio enterovirus has proven to be challenging to test for because on-the-spot tests cannot always perform the analysis necessary to attribute the virus to a particular strain of enterovirus or altogether different respiratory illnesses.
Applications for viral transport media beyond clinical diagnostics
While clinical diagnostics are the primary use of viral transport media, they are also critical in research and public health surveillance.
These applications include:
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Epidemiological studies: Transport media play a crucial role in tracking viral outbreaks and studying their spread.
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Vaccine development: Reliable sample transport ensures the integrity of specimens used in vaccine research and testing.
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Biobank storage: Preserving specimens for long-term research into emerging viruses and diseases.
This versatility underscores the importance of investing in high-quality viral transport systems.
Viral transport media price
Viral transport media can range in price, depending on a number of criteria, such as whether you are purchasing the transport media alone, a transport system, or a complete sampling kit. The viral transport medium price will also range based on the type of swab included in a sampling kit.
For product availability and viral transport media pricing, please check out our How to Buy page or contact your sales representative for assistance.
Choosing the right viral transport media for your needs
Selecting the appropriate viral transport media depends on several factors:
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Type of Specimen: Respiratory, enteric, or tissue samples may require different media to ensure viability.
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Testing Method: PCR, antigen detection, and culture testing each have specific compatibility requirements.
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Regulatory Compliance: Ensure that the media meets FDA or equivalent approvals, especially for specialized testing like SARS-CoV-2.
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Storage and Transport Conditions: Consider whether samples will be transported at room temperature, refrigerated, or frozen.
Consulting with an expert can help match your requirements with the ideal product.
Which Organisms Are Compatible with Viral Transport Medium?
A viral transport medium must do more than preserve a generic sample—it must protect the viability of specific pathogens long enough to allow for accurate identification, whether for clinical diagnosis or public health surveillance. Puritan’s UniTranz-RT® transport medium has been validated for a broad spectrum of viral organisms, making it a versatile choice across diagnostic settings.
Validated Organisms for UniTranz-RT®
The following pathogens have been tested and confirmed to remain viable for at least 48 hours at both refrigerated and room temperature (20–25°C) conditions when transported in Puritan’s UniTranz-RT® universal transport medium:
Respiratory and systemic viruses:
- Influenza A
- Respiratory syncytial virus (RSV)
- Herpes simplex virus types 1 and 2
Cytomegalovirus - Parainfluenza virus type 3
- Varicella-zoster virus
- Echovirus type 30
- Adenovirus
Intracellular and fastidious bacteria:
- Chlamydia pneumoniae
- Chlamydia trachomatis
- Mycoplasma pneumoniae
- Mycoplasma hominis
- Ureaplasma urealyticum
This breadth of compatibility ensures reliability not only for routine respiratory diagnostics but also for more specialized testing scenarios.
For a complete look at compatible viruses, view our product insert.
Applications for viral transport media beyond clinical diagnostics
While clinical diagnostics are the primary use of viral transport media, they are also critical in research and public health surveillance.
These applications include:
- Epidemiological studies: Transport media play a crucial role in tracking viral outbreaks and studying their spread.
- Vaccine development: Reliable sample transport ensures the integrity of specimens used in vaccine research and testing.
- Biobank storage: Preserving specimens for long-term research into emerging viruses and diseases.
This versatility underscores the importance of investing in high-quality viral transport systems.
Viral Transport Medium FAQ
What is the best viral transport medium for COVID-19 testing?
The best viral transport medium for COVID-19 testing is one that is specifically validated for use with SARS-CoV-2 diagnostic platforms, such as RT-PCR. Look for transport media that support RNA integrity and are compatible with molecular assays. Puritan’s UniTranz-RT® line, for example, is cited for use in SARS-CoV-2 testing and complies with CDC guidance for COVID-19 specimen collection.
How long can samples be stored in viral transport medium?
Samples stored in a viral transport medium can typically remain viable for 24 to 72 hours, depending on the medium’s formulation and the temperature conditions. Some media, including Puritan’s molecular preservation solutions, maintain sample stability at ambient temperatures for up to 30 days. Always refer to the product’s Instructions for Use (IFU) or package insert to confirm time and temperature limitations.
Is VTM the same as UTM?
While closely related, VTM (viral transport medium) and UTM (universal transport medium) are not identical. VTM is designed specifically for the transport of viral samples, often used in virology and public health testing. UTM is a broader formulation that may support both viral and bacterial specimen transport. When selecting between them, consider the type of pathogen being tested and any specific assay requirements.
Bacterial vs. Viral Transport Considerations
While viral transport media like UniTranz-RT® excel in maintaining RNA/DNA stability for viruses and intracellular pathogens, bacterial samples require a different formulation. Puritan’s Opti-Swab® Liquid Amies System includes a non-nutritive, thioglycolate-enriched medium specifically designed for preserving both aerobic and anaerobic bacterial specimens. If your testing scope includes bacterial culture, ensure you’re using the correct transport medium for optimal diagnostic recovery.
Viral Transport Medium Storage & Handling Best Practices
The performance of any viral transport medium depends not only on its formulation, but also on how it’s stored, handled, and used. Following best practices helps maintain specimen viability and reduces the risk of compromised results, especially when dealing with fastidious organisms or time-sensitive diagnostics.
Here are essential guidelines for storing and handling when using a viral transport medium:
Before Use
- Storage Temperature: Keep vials between 2–25°C (36–77°F) in a controlled environment. Do not freeze unless storing a collected specimen long-term.
- Visual Inspection: Before use, check the medium for color or clarity changes. A shift from pink to yellow or visible turbidity may indicate contamination.
- Package Integrity: Do not use if the vial, cap, or sterile packaging is damaged or past its expiration date.
During Specimen Collection
- Use Only Validated Swabs: Make sure you read your package insert to understand what swab is best to use alongside your viral transport medium. For example, UniTranz-RT® is validated for use with Puritan polyester or PurFlock Ultra® swabs. Avoid calcium alginate or wooden shafts, which can interfere with organism recovery.
- No Pre-Moistening: Swabs should not be pre-wet or bent prior to specimen collection.
- Aseptic Technique: Always collect and transfer samples using standard microbiological aseptic protocols to minimize contamination.
After Collection
- Immediate Placement: Place the collected sample into the transport medium immediately after swabbing.
- Secure Seal: Ensure the vial is tightly capped using the self-centering closure to prevent leakage or exposure.
- Label Clearly: Record relevant patient and sample information directly on the tube.
During Transport
- Refrigerate When Possible: For optimal recovery, keep samples refrigerated (4°C) during transport.
- Avoid Repeated Freeze-Thaw Cycles: For long-term storage, freeze at -70°C or colder, and minimize freeze-thaw episodes which degrade nucleic acid integrity.
- Transport Quickly: Process samples within 48 hours whenever possible to ensure accuracy.
Following these viral transport medium best practices supports high-quality results. Especially in high-stakes diagnostic environments where sample integrity is non-negotiable.
Viral transport media price
Viral transport media can range in price, depending on a number of criteria, such as whether you are purchasing the transport media alone, a transport system, or a complete sampling kit. The viral transport medium price will also range based on the type of swab included in a sampling kit.
For product availability and viral transport media pricing, please check out our How to Buy page or contact your sales representative for assistance.
Choosing the right viral transport media for your needs
Selecting the appropriate viral transport media depends on several factors:
- Type of Specimen: Respiratory, enteric, or tissue samples may require different media to ensure viability.
- Testing Method: PCR, antigen detection, and culture testing each have specific compatibility requirements.
- Regulatory Compliance: Ensure that the media meets FDA or equivalent approvals, especially for specialized testing like SARS-CoV-2.
- Storage and Transport Conditions: Consider whether samples will be transported at room temperature, refrigerated, or frozen.
Do you work in a medical practice, a hospital, a research facility, or a food processing operation? Are you responsible for collecting and transporting specimens to the lab? For the best results, you first need to choose the right tool.
Before you buy, consider these 4 questions:
Am I testing for a viral or a bacterial infection?
Virus and bacteria require different media to protect the microorganism for transport to the lab. Both media are commercially available. Puritan offers UniTranz-RT® for viral transport (and chlamydia, mycoplasma and ureaplasm) and Opti-Swab® for bacterial transport. These are available with swabs suitable for the collection site.
Is my mission to find one specific microorganism? Do I know what I’m looking for?
If yes, application specific media are available. Choose the transport media that is formulated to support and successfully transport the target microorganism. If you are testing for the presence of Group B Strep, choose a Lim broth product, such as Puritan’s LB-100. If you are checking an environment for the effectiveness of your sanitary process, consider Puritan’s ESK product, 25-83004 PD NB.
Could my problem be caused by any of a number of infectious microorganisms? Do I need a transport medium that will allow me to analyze for more than one?
Puritan’s UniTranz-RT® and Opti-Swab® products provide ample medium for multiple assays. Your processing method or system will be able to look at all material transported.
I am collecting DNA for a research project. I want the molecular specimen preserved intact for transport that may take several days from the field to the lab. Can I find this medium in a commercially available product?
Yes! Molecular transport media is readily available. Puritan’s PurSafe® has proven to reliably transport the specimen and is available with or without Puritan’s HydraFlock® specimen collection swab.
Planning ahead, I am involved in recommending automated specimen processing equipment for our facility. What questions do I need to ask about the specimen transport devices we will need for automated processing? Can I find transport media devices that will work for traditional processing now and then with an automated system, so the transition will be easy for our staff?
It is very important that you consider this carefully, as the investment in automated processing is significant. Consider the Opti-Swab® from Puritan. This device will perform well when testing for bacterial infection, whether processing by roll plate or automated system.
Consulting with an expert can help match your requirements with the ideal product.
Viral transport medium product examples
There are a number of different virtual transport medium products to meet the needs and price considerations. Selecting the right viral transport media depends upon the type of sample you’re transporting. Some of the most common viral transport products include:
Puritan UniTranz-RT® UT-317 Transport System
These may be used to transfer samples to laboratories for use in viral antigen detection test, PCR and rapid tests. These tubes may contain antimicrobial agents to minimize bacterial and fungal contamination, as well as glass beads that assist in releasing and dispersing the sample into the medium during laboratory vortexing.
One of Puritan’s most trusted universal transport medium kits, the UT-317 UniTranz-RT® system is engineered for versatility and reliability in viral diagnostics. This ready-to-use kit includes:
- A 3ml vial of universal transport medium stable at room temperature
- A PurFlock Ultra® ultrafine flocked swab with a 100mm molded breakpoint, ideal for nasopharyngeal and other precise sampling sites
- Leakproof self-centering cap for secure closure and easy swab removal
- Medical-grade plastic vial and cap for extended shelf life (18 months)
Each component is individually wrapped and sterile, ensuring compliance with IVD (in vitro diagnostic) use standards.
>> Check out Puritan’s UniTranz-RT line for a complete list of products.
How Puritan supports your diagnostic needs
At Puritan, we understand the challenges laboratories and healthcare providers face when ensuring sample viability. Our viral transport systems are designed with precision and reliability in mind. To ensure you have what you need, we offer:
- Customizable kits: Tailored solutions for specific diagnostic needs.
- Compliance and certification: Products that meet the highest industry standards, including FDA and CDC guidelines.
- Expert guidance: Dedicated support to help you select the right product for your unique requirements.
Whether you're navigating routine testing or responding to a public health emergency, Puritan is here to provide trusted solutions.
Why Comfort and Kit Design Matter in Viral Sample Collection
Sample collection can be uncomfortable for patients and difficult to perform consistently across staff. That’s why the design of the viral transport medium kit matters. Puritan’s patented PurFlock Ultra® swabs are engineered for high specimen yield with a soft-tip design that minimizes patient discomfort, especially critical during mass screenings or repeated testing scenarios.
The 100mm molded breakpoint ensures clean, reliable swab detachment, while the self-centering cap allows for safe, hands-free disposal and secure transport.
Reach out to Puritan today for viral transport media support!
For the most accurate diagnosis, it’s important to think beyond specimen collection and consider the journey your viral sample takes to the lab. Ensuring viability during this transport time is more critical than ever as laboratories manage higher testing demand even in the wake of the coronavirus pandemic.
If you’re not sure which viral transport media might be right for your specific needs, or best serve a broad range of uses, Puritan can help. Contact one of our experts with questions at any time.
