Human coronavirus NL63 (HCoV-NL63) is one of several human coronaviruses that commonly circulate globally. Discovered in the Netherlands in 2004 from a seven-month-old infant experiencing respiratory symptoms, it was identified as a novel Alphacoronavirus. This enveloped, single-stranded RNA virus is now recognized as a frequent cause of respiratory infections worldwide.
Common Illnesses and Symptoms
HCoV-NL63 infection can manifest in a range of clinical presentations, affecting both the upper and lower respiratory tracts. Individuals may experience mild, common cold-like symptoms such as cough, fever, runny nose, and sore throat. However, the virus can also lead to more severe conditions, particularly in vulnerable groups like young children, the elderly, and immunocompromised individuals.
More serious manifestations include bronchiolitis, pneumonia, and croup. HCoV-NL63 is a significant cause of croup in children. The virus is detected in approximately 1% to 10% of acute respiratory tract infections in children. It is also common for HCoV-NL63 infections to occur alongside other respiratory viruses, sometimes in over 50% of cases.
How HCoV-NL63 Spreads
HCoV-NL63 primarily spreads through respiratory droplets from coughs or sneezes. Direct contact, especially in densely populated environments, is also a mode of transmission. The virus can persist on contaminated surfaces, remaining infectious for up to seven days in secretions and about three hours on dry surfaces.
This coronavirus is found globally. Its prevalence often shows seasonal patterns, peaking during winter months in temperate climates. Infections can occur at any time of the year, with some regions reporting increased activity during spring and summer. Young children are particularly susceptible to HCoV-NL63 infection.
Distinguishing HCoV-NL63 from Other Coronaviruses
HCoV-NL63 is one of seven coronaviruses known to infect humans, including SARS-CoV and SARS-CoV-2. While HCoV-NL63 generally causes milder respiratory illnesses akin to the common cold, its shared characteristic with SARS-CoV and SARS-CoV-2 is its use of the Angiotensin-Converting Enzyme 2 (ACE2) receptor for entry into human cells. This shared receptor usage is a key biological feature.
Despite utilizing the same cellular entry point, HCoV-NL63 infection outcomes differ significantly from SARS-CoV and SARS-CoV-2. HCoV-NL63 typically results in mild to moderate infections, while SARS-CoV and SARS-CoV-2 can lead to severe, life-threatening respiratory diseases. This difference is partly due to HCoV-NL63’s weaker interaction with the ACE2 receptor. SARS-CoV-2 also infects and replicates more effectively in human respiratory cells than HCoV-NL63. HCoV-NL63 has circulated in humans for centuries, predating its discovery by an estimated 1000 years, establishing it as an endemic human coronavirus.
Diagnosis and Management
Diagnosing HCoV-NL63 infection can be challenging due to symptom overlap with other common respiratory viruses. The most reliable diagnostic method is reverse transcription polymerase chain reaction (RT-PCR) testing. This method is highly sensitive and specific, often integrated into broader respiratory panels that screen for multiple pathogens. Antibody detection assays can also indicate past exposure, with most individuals acquiring HCoV-NL63 infection during childhood.
Currently, no specific antiviral treatment or vaccine is available for HCoV-NL63. Management focuses primarily on supportive care to alleviate symptoms, including adequate rest, proper hydration, and over-the-counter medications for fever and pain. Using a room humidifier or taking a hot shower can help soothe a sore throat and cough. In severe cases requiring hospitalization, antiviral treatments may be considered, though a specific HCoV-NL63 antiviral is not yet approved. Individuals with concerning symptoms should seek medical attention.