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Coinfections of B. pertussis, respiratory viruses may just be coincidence
Heininger U. Pediatr Infect Dis J. 2011;doi:10.1097/INF.0b013e3182152d28.
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Coinfections of respiratory viruses and Bordetella pertussis may simply be a coincidence, based on prevalence of these illnesses circulating in the public, according to a study published online.
Ulrich Heininger, MD, and Marie-Anne Burckhardt, MD, both of the department of pediatric infectious diseases, University Children’s Hospital Basel in Switzerland, prospectively looked at ambulatory and hospitalized pediatric patients who were admitted to their hospital with a cough illness between Nov. 1, 2008, and Oct. 31, 2009. The researchers said University Children’s Hospital is the only children’s hospital in northwest Switzerland.
The researchers used nasopharyngeal aspirate specimens and polymerase chain reaction to measure rates of both viral and bacterial pathogens.
B. pertussis and B. parapertussis DNA “was amplified in 2% and 0.5% cases, respectively, of 1,059 [nasopharyngeal aspirate] specimens,” they said, noting that only two concomitant viruses and B. pertussis infections were identified out of a random sampling of 166 specimens, and those viruses were identified as respiratory syncytial virus and human metapneumovirus.
The researchers said higher rates of coinfection as reported in other studies are likely because those studies were conducted during periods of outbreaks and based on short-term observational studies.
“We would like to propose a simple hypothesis for the occurrence of such concomitant infections, namely coincidence,” the researchers wrote. “As B. pertussis has been shown to circulate in the population at high frequency, the detection of concomitant viral infections should not be surprising, despite the lack of a causal relationship.”
They said only prospective studies would be able to shed light on whether these confections occur based solely on chance or by some pathogenic interaction.
Disclosure: The researchers report no relevant financial disclosures.
Bordetella pertussis has been reported as an important cause of cough illness not only among infants, but also among older previously immunized individuals in whom it may be atypical and unrecognized. These observations led to the current recommendations in the United States for universal re-immunization with Tdap for children 11 years of age and older. However, in this prospective study from Switzerland, B. pertussis and B. parapertussis were rarely identified among over a thousand nasal pharyngeal aspirate specimens from children 0-17 years of age, despite the sensitive technique of PCR diagnosis.
This raises two important questions. First, what were the etiologies of the cough illnesses in these children and, second, how do we know an identified agent is the cause of the child’s symptoms? This study clearly indicates that viruses are the major cause of such coughing illnesses and that in about half of the children more than one virus may be concurrently present.
The recent development of new molecular technology and its increasing use have resulted in the recognition of previously unsuspected pathogens and the simultaneous development of more therapeutic options for viruses and other infectious agents. This increases the necessity to determine which is the pathogenic agent. Currently available methods to differentiate the culprit from the companion bystander have generally been limited and insufficiently studied. Determination of viral loads has been used for this purpose, but the correlation of the quantitative detection and clinical findings has been inconsistent, especially with viruses that are frequently shed for long periods among young children, such as some picornaviruses, adenoviruses and human bocaviruses. A single test that determines the pathogenicity has yet to be developed.
Ironically, the rapid advances in technology that allow the detection of new respiratory agents and therapeutic options simultaneously confound the development of rational management and augment the need for yet new diagnostic tests.
— Caroline Breese Hall, MD
Infectious Diseases in Children Editorial Board member
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