Editorial Commentary: Uncommon(ly Considered) Manifestations of Infection with Rhinovirus, Agent of the Common Cold

The first human rhinovirus was isolated ∼50 years ago from a person with a mild upper respiratory illness, and since that time, >100 serotypes have been identified. Experimental studies in human infection performed in the past 40 years have demonstrated that inoculation of a healthy susceptible adult with human rhinovirus leads to a self-limited upper respiratory tract illness, also known as the common cold. Epidemiologic studies have identified human rhinovirus as the most frequent cause of the common cold. Human rhinovirus infection causes >50% of colds in adults, and the prevalence may be >80% during the autumn season [1]. During the past 3 decades, human rhinovirus infection has been associated with a number of other clinical syndromes. These include bronchiolitis and pneumonia in children <5 years of age, exacerbations of asthma in older children and adults, exacerbations of chronic lung and heart disease in elderly adults, and pneumonia in immunocompromised patients [2–5]. Human rhinovirus infection in these patient populations can lead to significant morbidity, including the need for hospitalization and mechanical ventilation, and even to mortality. In many of these studies, human rhinoviruses were the first or second most frequent respiratory virus identified as a cause of disease. In this issue of Clinical Infectious Diseases, Louie et al. [6] report an outbreak of respiratory illness in a long-term care facility (LTCF) for elderly persons. Of the residents in 2 units, 100% were affected, as were 26 health care workers. Manifestations of illness among the residents included fever, productive cough, wheezing, and lethargy, and 15 residents (27%) had radiologic evidence of pneumonia. Twelve residents (21%) died of an acute infection. In contrast, the health care workers in the LTCF had only mild cases of respiratory illness. Rhinovirus was isolated from 7 of 13 residents, and 6 of these isolates were related to human rhinovirus type 82. A careful laboratory evaluation for other respiratory viruses, Mycoplasma pneumoniae, and Chlamydophila pneumoniae failed to identify another etiologic agent. Although Louie et al. [6] are careful to point out that their study was not designed to evaluate causality, the disease manifestations in the elderly patient population with significant comorbid conditions are consistent with other recent reports describing illnesses associated with human rhinovirus infection [2, 5]. Are the observations by Louie et al. [6] an uncommon manifestation of human rhinovirus infection, or are such illnesses more frequent than we realize and largely unrecognized? The increasing number of reports in the literature suggests that the latter may be the case. Cases of human rhinovirus infection are very common. The annual incidence in adults is estimated to be 1–2 infections per year, and the incidence in children is even higher. Traditionally, diagnosis of human rhinovirus infection has been made using cell culture. Although Louie et al. [6] were able to identify this outbreak using cell culture, the use of molecular diagnostic assays (RT-PCR) has significantly increased the number of cases of human rhinovirus infection identified in association with exacerbations of asthma and chronic lung disease [3, 4]. As molecular diagnostic assays become more readily available, cases of human rhinovirus infection may be recognized more commonly in association with other respiratory illnesses. The study by Louie et al. [6] suggests that human rhinovirus infection should be considered in persons with comorbid conditions and a severe, unidentified respiratory illness. One unsettling aspect of this outbreak was its prolonged course of 6 weeks and the apparently high attack rate among the staff of the LTCF. Although the investigation did not report possible routes of transmission among the residents, it would not be surprising if the health care workers played a significant role, as has been observed for other nosocomial respiratory virus infections [7]. The morbidity and mortality observed in the outbreak serve as a reminder of the potentially severe consequences of infection with an agent that only causes a mild respiratory illness in the health care worker. At the present time, infection-control measures are the only preventive strategies available for prevention and control of nosocomial outbreaks. Although measures to prevent cases of rhinovirus infection in health care institutions are not addressed in recent recommendations from the Centers for Disease Control and Prevention and Healthcare Infection Control Practices Advisory Committee [8], the measures suggested by Louie et al. (isolating and cohorting affected patients, restricting the rotation of staff between units, and limiting visitors [6]) are reasonable, especially in the context of an outbreak. Isolation measures should include both contact and droplet precautions. The increasing spectrum of disease associated with human rhinovirus infection highlights the need for strategies to prevent or treat these infections. The large number of human rhinovirus serotypes precludes the use of conventional vaccination strategies, even in an immunocompetent population. Several antivirals with activity against human rhinoviruses have been evaluated in clinical trials [9, 10]. The use of either IFN-α or pleconaril has been associated with decreases in the amount and frequency of the shedding of human rhinovirus, but the clinical utility of these drugs has been limited by their toxicities and modest clinical effects. The morbidity associated with human rhinovirus infection in high-risk patients increases the imperative to further develop and evaluate antiviral strategies for this population. Potential conflicts of interest. R.L.A.: no conflicts.