Using PCR to Detect Viruses in Blood and Tissue Samples
A 1989 patent by Nobel laureate Kary Mullis and his team on using polymerase chain reaction (PCR) to replicate and detect tiny amounts of viral DNA or RNA, such as HIV and Hepatitis B, directly from human clinical samples.
Original patent title: “Detection of viruses by amplification and hybridization”
A 1989 patent by Nobel laureate Kary Mullis and his team on using polymerase chain reaction (PCR) to replicate and detect tiny amounts of viral DNA or RNA, such as HIV and Hepatitis B, directly from human clinical samples. Granted to Hoffmann La Roche Inc in 1993 with 42 claims and 122 forward citations.
Key facts
Coverage
What does this patent actually cover?
This patent describes a method to detect viruses in human samples like blood or semen by copying their genetic material millions of times using Polymerase Chain Reaction (PCR). The process starts by mixing the sample with two short DNA starters called primers, free genetic building blocks (nucleoside triphosphates), and a copying enzyme (polymerase). First, the primers bind to the viral DNA if it is present. Next, the enzyme builds a copy of the target viral sequence. The mixture is then heated to separate the newly made strands, and the cooling and copying cycle is repeated multiple times to amplify the target sequence to detectable levels. Finally, a labeled probe binds to the amplified DNA to confirm the virus is present. For example, this method can detect HIV or Hepatitis B in a patient's blood sample without needing to grow the virus in a laboratory first.
The gap
What does this patent NOT cover?
- Does not cover detecting viruses using antibody-based tests (like ELISA) that do not amplify nucleic acids.
- Does not cover amplification techniques that do not use thermal denaturation to separate DNA strands (such as isothermal amplification).
- Does not cover genetic amplification of non-viral DNA, such as human genomic DNA or bacterial DNA.
- Does not cover methods that detect viral proteins rather than viral nucleic acids (DNA or RNA).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
Instead of trying to find a needle in a haystack, this method copies the needle millions of times until it is the only thing you see. It combined PCR amplification with specific hybridization probes to ensure that even a single viral particle in a complex biological sample could be reliably identified.
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Qualitative PCR tests for HIV-1 and Hepatitis B
Blood bank screening assays for viral contamination
Early infant diagnosis of HIV using dried blood spots
RT-PCR diagnostic kits for viral detection
Why it matters
The bigger picture
This patent laid the foundation for modern molecular diagnostics, enabling fast and highly sensitive testing for infectious diseases. Before this, detecting viruses like HIV required slow, difficult, and sometimes dangerous viral cultures. By allowing direct detection of viral genetic material in blood or semen, it revolutionized blood donor screening, clinical diagnostics, and viral load monitoring.
Filed
August 15, 1989
Granted
January 5, 1993
Market context
Who's building on this
Companies in this space
Hoffmann-La Roche, which acquired these PCR patents from Cetus, became the dominant player in molecular diagnostics. Other major diagnostics companies like Abbott Laboratories, Hologic, and Qiagen have built extensive portfolios of viral detection assays that rely on these foundational PCR amplification and hybridization principles.
Market impact
This patent helped establish the multi-billion dollar molecular diagnostics industry. It triggered a landmark transaction when Roche acquired Cetus's PCR patent portfolio for $300 million in 1991. The technology became the gold standard for blood supply safety, virtually eliminating transfusion-transmitted HIV and Hepatitis.
Claim 1 — Plain English
What this patent covers
This patent describes a method to detect viruses in human samples like blood or semen by copying their genetic material millions of times using Polymerase Chain Reaction (PCR). The process starts by mixing the sample with two short DNA starters called primers, free genetic building blocks (nucleoside triphosphates), and a copying enzyme (polymerase). First, the primers bind to the viral DNA if it is present. Next, the enzyme builds a copy of the target viral sequence. The mixture is then heated to separate the newly made strands, and the cooling and copying cycle is repeated multiple times to amplify the target sequence to detectable levels. Finally, a labeled probe binds to the amplified DNA to confirm the virus is present. For example, this method can detect HIV or Hepatitis B in a patient's blood sample without needing to grow the virus in a laboratory first.
The clever bit
Instead of trying to find a needle in a haystack, this method copies the needle millions of times until it is the only thing you see. It combined PCR amplification with specific hybridization probes to ensure that even a single viral particle in a complex biological sample could be reliably identified.
What it does not cover
- Does not cover detecting viruses using antibody-based tests (like ELISA) that do not amplify nucleic acids.
- Does not cover amplification techniques that do not use thermal denaturation to separate DNA strands (such as isothermal amplification).
- Does not cover genetic amplification of non-viral DNA, such as human genomic DNA or bacterial DNA.
- Does not cover methods that detect viral proteins rather than viral nucleic acids (DNA or RNA).
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
PatentBrief Score
Impact Score
Strong
Citation count
40/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$270K – $864K
Midpoint $540K · expired or expiring · industry ×3.0
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
42 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Mullis, K. B., Sninsky, J. J., Ehrlich, H. A., Mack, D. H., & Kwok, S. Y. (1993). Using PCR to Detect Viruses in Blood and Tissue Samples (U.S. Patent No. 5,176,995). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/5176995/hiv-pcr-detection
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does Using PCR to Detect Viruses in Blood and Tissue Samples cover?
A 1989 patent by Nobel laureate Kary Mullis and his team on using polymerase chain reaction (PCR) to replicate and detect tiny amounts of viral DNA or RNA, such as HIV and Hepatitis B, directly from human clinical samples.
Who owns patent US 5176995?
Hoffmann La Roche Inc owns this patent, granted in 1993.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 5176995 cited by?
This patent has been cited by 122 later patents that build on its ideas.
What problem does this patent solve?
This patent laid the foundation for modern molecular diagnostics, enabling fast and highly sensitive testing for infectious diseases. Before this, detecting viruses like HIV required slow, difficult, and sometimes dangerous viral cultures. By allowing direct detection of viral genetic material in blood or semen, it revolutionized blood donor screening, clinical diagnostics, and viral load monitoring.
What does this patent NOT cover?
Does not cover detecting viruses using antibody-based tests (like ELISA) that do not amplify nucleic acids.
Same assignee
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