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We have already talked about ongoing influenza pandemics and its threat to health via our previous blog posts. We have also mentioned that viral-bacterial coinfections are a commonly encountered illness. Even though we cannot present you an accurate number for these coinfections due to lack of reporting systems, bacterial pneumonia is estimated to complicate from 0.5% to 6% of influenza patients. The considerable amount of bacterial pneumonia as a postviral complication shows us the importance to investigate these infections together, and also the fact that it remains a significant source of morbidity and mortality.

Epidemiologically, Streptococcus pneumoniae and Staphylococcus aureus (both methicillin-sensitive S aureus and methicillin-resistant S aureus) are most common. However, infections in humans are often polymicrobial, involving combinations of multiple viruses and/or bacteria. Therefore it would not be wise to attribute one infection to only one bacteria or virus, rather coinfections should be investigated. We would like to present a table created by Prasso and Deng (2017) for common viral-bacterial coinfections and their associated clinical infections in human hosts:

(Respiratory) Virus

Known bacterial coinfections

Associated secondary infections

Influenza

S pneumonia

  • Pneumonia
  • Otitis media
  • Sinusitis
  • Meningitis

S aureus

S pyogenes

H influenza

Moraxella catarrhalis

Neisseria meningitidis

Respiratory syncytial virus

S pneumonia

  • Pneumonia
  • Bronchitis/bronchiolitis

Adenovirus

S pneumonia

  • Pneumonia

H influenzae

M catarrhalis

Coronavirus

H influenzae

  • Pneumonia

Human rhinovirus

S pneumoniae

  • Pneumonia
  • Sinusitis
  • Otitis media

H influenzae

S aureus

M catarrhalis

Parainfluenza virus

S pneumoniae

  • Pneumonia

M catarrhalis

Human metapneumovirus

S pneumoniae

  • Pneumonia
  • Bronchitis

Measles virus

S pneumoniae

  • Otitis media
  • Pneumonia
  • Tracheobronchitis

S aureus

H influenzae

I can see your confusion after reading so many strange microbe names. Don’t be so confused, you didn’t think that influenza was the only virus that infects humans, right? However it gets even more confusing when we think about the combinations between those microbes and also their associated secondary infections. But we are not here to diagnose anyone, so it is just better to know that there can be various reasons behind our illnesses. And also pneumonia, one of the most common infectious complications of respiratory viruses, is one of those to look after.

We know from the scientific reviews that viral infections increase the susceptibility of secondary bacterial pneumonias. We should also consider  the fact that microbiologic and epidemiologic factors can contribute to the pathogenesis of these coinfections. To prevent and treat we are still looking after influenza vaccination and also antibiotics or antivirals. These strategies are one of those that you should talk with your doctor. If you would like to understand your respiratory health status from the comfort of your home and decide whether you need to go to the doctor or not, you can always download the FluAI app from the App Store or Play Store. 

References:

Prasso, J. E., & Deng, J. C. (2017). Postviral Complications. Clinics in Chest Medicine, 38(1), 127–138. doi:10.1016/j.ccm.2016.11.006  

Author

Elif Başak Alço

PM & CLINICAL TEAM

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