Table 1.
Characteristics of infectious agents associated with asthma exacerbations
| Pathogen | Family | Type | Number of serotypes | Seasonality | Frequency of cause of common cold in adults [6] |
|---|---|---|---|---|---|
| Rhinovirus | Picornaviridae | RNA virus | 100+ | Year round with fall and spring peaks | 45% |
| Coronavirus | Coronaviridae | Enveloped RNA virus | 3 | Year round with winter peak. Summer outbreaks have been described. | 25% |
| Influenza virus | Orthomyxoviridae | Enveloped RNA virus | 3 | Annual epidemic in winter in temperate climates. In tropical climates there may be multiple outbreaks. | 14% |
| Adenovirus | Adenoviridae | Double-stranded, non-enveloped DNA virus | 49 | Sporadic. Epidemics and endemic disease are more prevalent in the late winter, spring, and summer. | 5% |
| Parainfluenza virus | Paramyxoviridae | Enveloped RNA virus | 4 | Winter peaks for Parainfluenza 1 and 2; summer peaks for Parainflunza 3 | 5% |
| Respiratory syncytial virus | Paramyxoviridae, but lacks neuraminidase and hemagglutinin surface glycoproteins | Enveloped RNA virus | 2 (A and B) | Epidemics are mainly in winter and early spring but may be sporadic throughout the year. | 1% |
| Human metapneumovirus | Paramyxoviridae | RNA virus | 2 | It was initially thought that epidemics occurred between December and April; however, it has been extended to all year round. | Unknown |
| Mycoplasma pneumoniae | Smallest free-living microorganisms | 1 | Pleomorphic and ubiquitous in animals and plants; prone to outbreaks throughout the world, at any season | ||
| Chlamydia pneumoniae | Antigenically, genetically, and morphologically distinct from other Chlamydia species. | All isolates seem to be closely related serologically. | 1 | Worldwide distribution, with no evidence of seasonality or known animal reservoir | |
| A new name has been proposed: Chlamydophila pneumoniae |