Human rhinovirus (HRV) and enterovirus (EV) are common viral pathogens. Though often causing mild illnesses, these viruses belong to the same family but can lead to varied health impacts. Understanding their characteristics helps differentiate their potential effects on the body.
Human Rhinovirus: The Common Cold Culprit
Human rhinovirus is the most common cause of the common cold. It is a small, non-enveloped RNA virus belonging to the Picornaviridae family. There are over 100 serotypes, with over 165 distinct types across its three species (HRV-A, HRV-B, and HRV-C). This contributes to the frequent occurrence of common colds throughout a person’s life.
HRV thrives at cooler temperatures, around 32-33°C, making the upper respiratory tract an ideal environment. While most infections are mild, they can trigger more severe conditions. HRV is a significant cause of asthma exacerbations and can lead to lower respiratory tract infections like bronchitis and pneumonia, especially in vulnerable populations such as infants, the elderly, and those with weakened immune systems.
Enterovirus: Beyond the Common Cold
Unlike rhinoviruses, enteroviruses are associated with a broader spectrum of clinical manifestations, capable of infecting multiple body systems beyond the respiratory tract. The genus Enterovirus includes types such as Coxsackieviruses, Echoviruses, and Poliovirus.
Enteroviruses prefer warmer body core temperatures, allowing them to replicate effectively in various internal organs. This enables them to cause a diverse range of illnesses affecting the gastrointestinal tract, central nervous system, skin, and heart. While some infections are asymptomatic, others can result in noticeable symptoms and, in some cases, severe disease.
Shared Characteristics and Key Distinctions
Both human rhinoviruses and enteroviruses are small, non-enveloped viruses with a single-stranded RNA genome, belonging to the Picornaviridae family. Their capsids, or protein shells, are composed of 60 protein subunits, making them structurally similar. Both types are highly contagious, contributing to their widespread presence in human populations.
Despite these similarities, key distinctions set them apart. Human rhinoviruses predominantly infect the upper respiratory tract, leading primarily to common cold symptoms. In contrast, enteroviruses can infect a wider range of body systems, including the gastrointestinal tract, central nervous system, skin, and heart. This difference in tissue tropism results in varied clinical syndromes; while rhinoviruses are largely limited to the common cold, enteroviruses can cause conditions such as hand-foot-and-mouth disease, viral meningitis, and myocarditis.
Their optimal replication temperature also differs: rhinoviruses prefer cooler temperatures around 32-33°C, typical of nasal passages, whereas enteroviruses thrive at the warmer 36-37°C body core temperature. Furthermore, enteroviruses are acid-stable, enabling them to survive the acidic environment of the stomach and infect the intestinal tract, a characteristic not shared by rhinoviruses, which are acid-labile.
Manifestations and Transmission
Human rhinovirus infections manifest as the common cold, with symptoms appearing one to three days after exposure. These symptoms include a runny or stuffy nose, sneezing, sore throat, and cough. Some individuals may also experience mild body aches or a low-grade fever. The nasal discharge may start clear and become thicker or discolored, which is a normal progression of the illness.
Enterovirus infections present a varied array of symptoms depending on the specific type and the affected body system. Hand-foot-and-mouth disease, caused by certain enteroviruses like Coxsackievirus A16, features painful mouth sores and a rash with spots or blisters on the hands, feet, and sometimes buttocks. Viral meningitis, an inflammation of the membranes surrounding the brain and spinal cord, can cause sudden fever, headache, and a stiff neck. Myocarditis, an inflammation of the heart muscle, may lead to chest pain, fatigue, shortness of breath, and irregular heartbeats.
Both viruses spread through respiratory droplets released when an infected person coughs or sneezes, as well as through close personal contact. Indirect transmission occurs by touching contaminated surfaces (fomites) and then the eyes, nose, or mouth. A key distinguishing transmission route for enteroviruses is the fecal-oral pathway, common through contact with infected stool, contaminated food or water, or unwashed hands.
Diagnosis, Management, and Prevention
Diagnosis of rhinovirus infections is often based on clinical symptoms, as laboratory testing is not necessary for mild cases. For severe enterovirus infections, healthcare providers may use laboratory tests such as polymerase chain reaction (PCR) or viral culture to identify the virus. In cases of suspected viral meningitis, a spinal tap may be performed to analyze cerebrospinal fluid.
No specific antiviral treatments are available for most rhinovirus and non-polio enterovirus infections. Management focuses on supportive care to alleviate symptoms. This includes getting adequate rest, staying hydrated, and using over-the-counter medications to relieve symptoms like fever, pain, and congestion.
Preventive measures are important for both viruses. Frequent handwashing with soap and water, especially after coughing, sneezing, or using the restroom, helps reduce transmission. Avoiding close contact with sick individuals and refraining from touching one’s face with unwashed hands can also limit spread. Regularly cleaning and disinfecting frequently touched surfaces helps eliminate viral particles. While no vaccine exists for common rhinoviruses or most non-polio enteroviruses, the polio vaccine is a notable exception, effectively preventing poliomyelitis caused by poliovirus.