John Bartlett's Game Changers in Infectious Disease: 2011

John G. Bartlett, MD


October 26, 2011

In This Article

Pandemic Influenza

Following the first major report of the 2009-2010[45] pandemic influenza, influenza will never be the same. The report included a detailed account of 18 relatively young patients from a total of 98 patients with laboratory-confirmed influenza who were hospitalized at the National Tertiary Hospital for Respiratory Illnesses in Mexico City. Of these 18 patients, 12 required mechanical ventilation and 7 died. Subsequent events led to a massive scientific attack on influenza, substantial changes in our understanding of the disease, policies in dealing with influenza epidemics, changes in public health policy, and new recommendations for management.

Why Is This a Game Changer?

  • This epidemic was humbling; it was declared a pandemic, but no one seemed to be able to define "pandemic."[46] Perhaps more important is that no one saw it coming. The expectation of a pandemic was correct, but it was supposed to come from Asia where we have the surveillance system set up. It was expected to involve a new strain of influenza (such as H5N1) and to be highly lethal. Instead it came from Mexico, involved the oldest strain of influenza (H1N1), and had low mortality.

  • We rapidly learned that our vaccine production supply was not very efficient and this led to an ambitious attempt to improve the product and reduce the time required for delivery using alternative systems.[46]

  • Urgency for diagnostic testing coincided with the surge in technology for point-of-care testing and molecular diagnostics, and both were applied to influenza with fervor. The point-of-care test proved to be quite successful in specificity but was relatively poor in sensitivity; in fact, clinical judgment seemed to be superior to the available point-of-care test.[47] Molecular PCR testing requires 1-2 hours and, compared with culture, actually emerged as the gold standard for diagnosis. The main disadvantages are the need for laboratory technicians and cost.

  • The attention on this pandemic prompted multiple historic reviews of previous pandemics including the 1918-1919 pandemic that exceeded all others in terms of global morbidity and mortality. Influenza pundits engaged in a continuous debate over the major cause of death in that pandemic; was it bacterial superinfection (which would be less problematic in the antibiotic era), or was it simply viral pneumonia? Ambitious gumshoe detective work with historic reports and autopsy studies determined that the major cause of death was bacterial infection with the following pathogens: S pneumoniae, N meningitidis, H influenzae type B, S aureus, and group A streptococci.[48] Translated to the 2011 experience, the major bacterial superinfecting pathogens were S pneumoniae, group A streptococci, and S aureus, which proved prophetic in the subsequent CDC review.[49]

  • A raging debate arose over the requirements for masks by healthcare workers. The CDC and Institute of Medicine recommended the N95 mask.[50] This was bad news because the N95 masks required fitting, were relatively expensive, were in short supply, and were uncomfortable to wear because of difficulty breathing through them. The definitive study was finally conducted showing that surgical masks were equally good, and this made the N95 masks almost totally antiquated except for special procedures such as bronchoscopy.[51]

  • The issue of mandatory healthcare worker vaccination came to a head during the 2009 influenza pandemic. The review of the record indicated successful vaccination in only about 62% of healthcare workers in the United States.[52] However, the momentum for mandatory use of the vaccine came from proven benefit, vaccine safety, ethical principles, and legal precedent.[53,54]

  • Influenza vaccine recommendations from the CDC had a history of increasing inclusions, on the basis of risk, that seemed to continually expand the targeted population until the 2009 pandemic when the Advisory Committee on Immunization Practices finally went all the way and recommended the vaccine for all persons over the age of 6 months.[55]

What Does This Mean to the Practitioner?

Oseltamivir and zanamivir remain the only anti-influenza drugs that are generally recommended, and oseltamivir seems to have the decided edge because of its oral delivery system. We have all learned that the window of opportunity for impact on disease course is during the first 48 hours, but the more recent guidelines, based largely on the 2009 pandemic experience, are much more aggressive. Although early treatment is urged, patients who are seriously ill with influenza or at high risk for serious illness (chronic heart, lung, renal, neurologic, or liver disease) should be treated on the basis of clinical observation. The recommendation is to use this agent regardless of the duration of symptoms.[56]