The Role of Parainfluenza Viruses in Severe Respiratory Infections
Amesh A. Adalja, MD, FACP, FACEP, FIDSA, December 1, 2017
It is widely assumed that the most likely manifestation of a pandemic will be a respiratory illness. Severe acute respiratory infections abound in hospitals, and many of these are caused by viruses. Several viral families have the capacity to cause severe acute respiratory infections, and it is important to understand the epidemiology of the viruses that cause severe respiratory infections not only to optimize patient care but to have situational awareness for changes in viral behavior.
Among the viruses that cause respiratory infections are the human parainfluenza viruses (HPIVs). This group of RNA viruses, which are part of the paramyxovirus family that also includes viruses such as RSV, Nipah, Hendra, and metapneumovirus, consists of 4 strains (1-4).
A new study published in Influenza and Other Respiratory Viruses provides insight into the role of human parainfluenza viruses in severe acute respiratory infections in China.
More than 1,200 Beijing-Area Hospital Inpatients Studied
In this study, which was conducted between 2014 and 2016, Pan and colleagues randomly selected 1,229 inpatients from 11 different urban and suburban hospitals in the Beijing area who were hospitalized with fever and cough and had a symptom duration of 10 days or fewer. Of these patients, 81 (6.6%) were positive for parainfluenza virus, with the majority being positive for HPIV-3. Coinfections with other viruses--most commonly rhinovirus--occurred in 18 (1.4%) patients. Isolation of HPIVs was most common in the month of August, and children younger than 5 years old or adults over 60 were the most common age groups infected.
Over 6% of severe acute respiratory cases in those over 60 were caused by HPIVs. The HPIV-3 isolates were all from the same viral cluster (C), and some genetic drift was noted from prototypical strains in the HN gene with the emergence of a dominant subgroup. Compared to other etiologies of severe acute respiratory infection, those infected with HPIV tended to have better outcomes in terms of ICU admission or death.
The Importance of Epidemiology
In clinical medicine, there is a tendency to underplay the role of respiratory viruses for which there is no specific therapeutic intervention, because a specific diagnosis does not strictly change clinical management. HPIVs fall into this category and are often not diagnosed except in immunosuppressed hosts. However, HPIVs--and many other viruses that cause respiratory syndrome--have strong clinical import.
Pan and colleagues provide important data for understanding the current role of HPIVs with respect to severe acute respiratory infections. In future surveillance activities, it will be interesting to determine any change in the epidemiologic or genetic trajectory of HPIVs that may occur and to understand what the clinical and pandemic preparedness implications may be. When studying respiratory viruses, it is essential to recall the lessons of the coronavirus family, long neglected prior to the emergence of SARS and MERS. Having real-time insight into the clinical impact and ongoing genetic changes of the myriad respiratory viruses should be a core component of pandemic preparedness.
Pan Y, Zang Y, Shi W, et al. Human parainfluenza virus infection in severe acute respiratory infections in Beijing, 2014-2016: a molecular epidemiological study. Influenza Other Respir Viruses 2017;11:564-568.