The common cold is a familiar ailment, and the viruses behind it often cause confusion. Human Rhinovirus (HRV) and Enterovirus (EV) are two terms frequently encountered when discussing respiratory illness, sometimes used interchangeably, which obscures their true relationship. While both are highly common pathogens, a closer look at their biology and the spectrum of diseases they cause reveals important distinctions. Understanding the unique characteristics of each virus, particularly their potential for causing systemic illness, is key to differentiating these two sources of infection.
Shared Viral Family and Classification
Human Rhinovirus and Enterovirus are closely related, tracing their lineage back to the same parent group, the Picornaviridae family. This family of viruses is characterized by its members being small, non-enveloped, and containing a single-stranded RNA genome with positive polarity. Their diminutive size, ranging from approximately 20 to 30 nanometers, is reflected in the family name, which comes from the Latin word “pico,” meaning small.
Within the Picornaviridae family, both HRV and EV are classified under the genus Enterovirus. This close genetic relationship and shared physical structure explain why they are often grouped together in clinical settings and diagnostic tests. Molecular assays, such as polymerase chain reaction (PCR), frequently rely on genetic targets common to both, leading to results that report them as a combined “rhinovirus/enterovirus” positive.
Human Rhinovirus Specifics
Human Rhinovirus is recognized as the single most frequent cause of the common cold, responsible for over half of all cold-like illnesses globally. This virus is characterized by its preference for the cooler temperatures found in the nasal passages and upper respiratory tract. It typically remains localized to the nose, throat, and sinuses, which dictates its generally milder clinical presentation.
The symptoms of an HRV infection are classic cold complaints, including a runny nose, nasal congestion, sneezing, and a sore throat. While often self-limiting, these infections are responsible for millions of missed work and school days each year. HRV rarely causes severe complications in healthy individuals, but for people with pre-existing conditions, particularly asthma, it can trigger acute exacerbations and significant breathing difficulty.
Enterovirus Spectrum of Illness
The primary clinical distinction between the two groups lies in the Enterovirus’s ability to spread beyond the respiratory tract and cause systemic disease throughout the body. While many EV types can cause symptoms indistinguishable from a common cold, their defining trait is their potential to target tissues outside of the upper airways. This capability means that Enteroviruses are associated with a much wider and often more severe spectrum of illness.
Once an Enterovirus moves past the initial site of infection in the respiratory or gastrointestinal tract, it can enter the bloodstream and spread to other organs. This systemic tropism allows certain strains to cause serious neurological conditions, such as aseptic meningitis, which is inflammation of the membranes surrounding the brain and spinal cord. Other Enterovirus types are well-known for causing rashes, herpangina (blisters in the throat), and hand-foot-and-mouth disease.
More severe, though less common, manifestations include myocarditis, an inflammation of the heart muscle, and acute flaccid myelitis (AFM), a rare but serious neurological condition that affects the spinal cord and can cause sudden muscle weakness. Enterovirus D68 (EV-D68) is a specific type known to cause severe respiratory illness, particularly in children with asthma, and has been linked to outbreaks of AFM.