The “lung infections” category includes “Influenza and pneumonia” (ICD–10 codes J10–18) and “Other acute lower respiratory infections” (ICD–10 J20–22), but it excludes “Tuberculosis” (ICD–10 A15–19) and “HIV disease resulting in infectious and parasitic diseases” (ICD–10 B20). By excluding respiratory tuberculosis as well as pneumonias in patients with HIV/AIDS, these statistics might be considered by some to underestimate the burden of disease due to lung infections. Even with those exclusions, lung infections accounted for more than 6% of the total global burden of disease in 2002. This disease burden is greater than that of other better-recognized causes of disease (Figure 1). This impressive burden is not an anomaly of that particular year, due to SARS or any other unusual epidemic or event, but is instead the norm. Since 1990, when WHO began compiling and presenting such statistics, lung infections have consistently caused more burden than any of the diseases identified in Figure 1 [3,4].

For those in wealthier populations, little further advancement is evident against lung infections. Focusing exclusively on the highest income populations (“Established Market Economies” or “High Income” groups in the WHO Burden of Disease Study), a comparison of the relative DALY losses due to lung infection shows little change from 1990 to 2002 (151 and 137 DALYs lost/100,000 population, respectively), whereas there have been dramatic improvements in the burdens due to other diseases within these wealthy communities. For example, among the wealthiest populations, HIV in 2002 caused less than half the disease it did in 1990 (from 159 to 72 DALYs lost/100,000 population). There are no DALY statistics available prior to 1990, but other indicators such as the US mortality rate due to pneumonia and influenza suggest that, for wealthy countries, there has been little or no progress against lung infections since the first half of the last century [6].

Determining whether funds are contributing to research against a given disease is horribly inexact. Furthermore, the conceptual advances with most promise against a particular disease may more likely result from basic research than from disease-focused research. However, substantial resources are allocated to understanding and fighting particular diseases, and biomedical progress against those diseases is influenced by these targeted efforts. While the greatest burdens of disease and the greatest threats to the public health might be presumed to receive the greatest shares of research funding, they do not.

The US National Institutes of Health (NIH) spent approximately US$28 billion on health-related research in 2004 [13], of which US$287 million was allocated to lung infections. This is substantive and laudable, but it must be considered in perspective. It pales in comparison with the US$1.63 billion spent on biodefense. More NIH money is spent on smallpox research (US$324 million) alone than on lung infection research. While it is essential to be proactive in recognizing, preventing, and preparing for looming or emerging threats to public health, it may be questioned whether funding for speculated risks should so overwhelm funding for diseases already causing such tremendous burdens.

Lung infection research is also poorly funded when compared with other currently significant public health concerns. For example, US$2.85 billion were spent on HIV/ AIDS research, which is substantively improving prospects against this very important disease. It is remarkable, though, that lung infections cause a comparable or greater disease burden (Figures 1 and ​and2),2), yet they receive only one-tenth of HIV/AIDS research funding. In a similar vein, the NIH allocated comparable resources to lung infections as to sexually transmitted diseases (US$237 million), even though in wealthy countries such as the US lung infections cause seven times more disease than do sexually transmitted diseases (Figure 2), with even larger differentials in poorer countries. These figures from the NIH are but a few examples demonstrating that lung infections are relatively under-represented.

Reacting to the pandemic threat of the recently emerging avian influenza virus (H5N1), the president of the US recently requested a lump sum totaling US$7.1 billion [14]. The majority of requested funds in the president's plan, more than US$5.3 billion, would be slated for the manufacture, purchase, and stockpile of vaccines and antivirals targeting influenza. An additional US$0.8 billion would be allocated for research on new vaccines and antivirals against influenza, US$0.6 billion for influenza preparedness planning, and US$0.3 billion to help countries detect and contain influenza outbreaks. It is this author's opinion that the immediate need for such immense resources results from the potential of a severe influenza pandemic combined with many years of inadequate attention to lung infections. As of the time of writing this essay, the US Congress has yet to approve funding, and it remains unclear how much will be approved and how it will be deployed if approved, but a discrete set of funds may soon become available for fighting influenza specifically.

While the idea of fighting against a specific microbe is attractive, and such an “us-against-them” mentality is effective at mobilizing commitments, a microbe-specific focus is appropriate for some infectious diseases more than others. Lung infections do not result from one or a few extremely virulent microbes especially adapted to living in our lungs. Rather, a tremendous variety of microbes causes lung infections, and a strategy focused on the microbes is destined to be a game of catch-up. The physiology of breathing requires our lungs to be enormously exposed to microbes, both from the external environment (the air) and from a microbe-rich part of our own anatomy (our upper airways). It is inevitable that microbes land in our lungs. In part for these reasons, respiratory infections are common, and new respiratory pathogens are likely to emerge frequently. Eliminating microbes in the lungs requires inflammatory responses that by their very nature compromise ventilation and blood-gas exchange. Thus, eliminating infection threatens physiology, and in part for this reason respiratory infections are often severe.