Rhinovirus: The Biological Profile of the Common Cold Agent
Rhinoviruses are the primary culprits behind the common cold, responsible for at least 50% of all cold infections, with some estimates suggesting they account for as many as 80%. These tiny but highly efficient pathogens are part of the larger Enterovirus genus and play a significant role in human respiratory health across the globe.
![Maximum likelihood phylogenetic trees of enterovirus species A, B, C, D and rhinovirus A, B, C isolates from Latin America. The 5'UTR region is much more affected by recombination events than the VP4/VP2 coding sequence. The paraphyletic nature of "rhinovirus" is visible.[31]](/images/30/83/3083e8b2a745349dd7fde232f3225e4ab4780b5da076258b31cebdd1908c1f96.jpg)
Key Facts
- Primary Cause: Responsible for 50% to 80% of common cold cases.
- Size: Extremely small, with a diameter of approximately 30 nanometers.
- Preferred Temperature: Replicates most effectively at 33 °C (91.4 °F).
- Transmission Rate: Has an estimated basic reproduction number (R0) in excess of 2.5.
- Medical Status: As of September 2025, there are no FDA-approved vaccines or antiviral treatments.
Scientific Classification and Taxonomy
Rhinoviruses belong to the realm Riboviria, kingdom Orthornavirae, and phylum Pisuviricota. Within the family Picornaviridae, they are classified under the genus Enterovirus. While many taxa are traditionally associated with enteroviruses, the rhinovirus group is specifically divided into three distinct species based on genetic diversity.
The Three Rhinovirus Species
The International Committee on Taxonomy of Viruses (ICTV) classifies rhinoviruses into three main species. Since 2020, new types are categorized based on the genetic diversity of their VP1 gene rather than just serotypes. The recognized species are:
- Rhinovirus A (Enterovirus alpharhino)
- Rhinovirus B (Enterovirus betarhino)
- Rhinovirus C (Enterovirus cerhino)
Together, these species include at least 165 recognized types. While Species A and B share a similar indexing system, Species C utilizes its own separate index.
Viral Structure and Genome
Rhinoviruses are non-enveloped viruses with a dodecahedral (twelve-sided) structure. They are among the smallest known viruses; for comparison, influenza viruses are roughly 80–120 nanometers, and smallpox is about 300 nanometers. Their genome consists of single-stranded positive-sense RNA, ranging from 7,200 to 8,500 nucleotides in length.
The Capsid and Protein Composition
The viral particle, or capsid, is composed of 60 copies each of four structural proteins: VP1, VP2, VP3, and VP4. VP1, VP2, and VP3 form the primary exterior of the capsid, which serves as the target for antibodies. The much smaller VP4 protein is located at the interface between the capsid and the RNA genome. The structure was famously determined in 1985 using x-ray crystallography.
| Virus Type | Approximate Diameter (nm) |
|---|---|
| Rhinovirus | 30 |
| Influenza | 80–120 |
| Smallpox/Vaccinia | ~300 |
Epidemiology and Transmission
Rhinoviruses can be detected year-round, but they exhibit clear seasonality. In the northern hemisphere, incidence peaks between September and April. This seasonality is likely driven by the start of the school year, increased time spent indoors, and lower ambient temperatures. Because rhinoviruses prefer a replication temperature of 33 °C (91.4 °F), they tend to infect the upper respiratory tract, which is cooler than the core body temperature of 37 °C.
The virus spreads efficiently, with an R0 value exceeding 2.5. A significant portion of infections are asymptomatic, occurring in approximately 15–30% of children and up to 50% of adults. While anyone can be infected, infants, the elderly, and immunocompromised individuals are often the most affected.
Viral Interference
Interestingly, rhinovirus infections can exhibit negative interference with other viruses like influenza. Research suggests that a rhinovirus infection can trigger an immune response that significantly reduces the presence of influenza viral RNA if an influenza infection occurs shortly thereafter.
Frequently Asked Questions
Why do rhinoviruses cause the common cold?
Rhinoviruses are the primary agents responsible for the common cold, causing between 50% and 80% of all cold-related infections by targeting the upper respiratory tract.
Why is the infection more common in winter?
Seasonality is influenced by people spending more time indoors and lower outdoor temperatures. Additionally, the virus replicates more effectively at the slightly cooler temperatures (33 °C) found in the upper respiratory tract.
Is there a vaccine for the common cold?
As of September 2025, there are no FDA-approved vaccines or specific antiviral treatments available for rhinovirus infections.
How many types of rhinovirus are there?
There are at least 165 recognized types distributed across three species: Rhinovirus A, B, and C.
How does rhinovirus compare to influenza in size?
Rhinoviruses are significantly smaller, measuring about 30 nanometers in diameter, whereas influenza viruses typically range from 80 to 120 nanometers.