The multitude of factors that influence what illness or disease strike are sometimes quite surprising

The multitude of factors that influence what illness or disease strike are sometimes quite surprising

As noted in prior posts, the key issue in toxic torts is causation.  Yet, how an illness, disease, or adverse impact occurs is sometimes quite surprising.  Only to illustrate the principle, I note two recent reports that demonstrate the unexpected.

Researchers have long puzzled over why flu becomes so much more active in winter. A new study reveals that dry air is one likely culprit.  Scientists have proposed different explanations for why influenza makes more people sick in temperate regions during winter.  One idea is that people simply spend more time indoors together because it's colder, giving the virus more opportunity to spread.  Another idea is that environmental factors affect the survival and transmission of the virus.  For example, laboratory studies have found that higher temperatures affect the flu virus's coat.  That could potentially explain why flu doesn't spread during summer, but temperatures indoors, where most Americans spend the bulk of their time, are often tightly controlled.

Relative humidity is another suspect, but the data have not established a strong link between relative humidity and flu outbreaks.  [Relative humidity is not a measure of the actual amount of moisture in the air, but how close the air is to the point at which a "cloud" would start to form.] Researchers decided to look more intensely at this issue.  They reexamined laboratory data and found that absolute humidity could account for the airborne survival and transmission of the virus.

The researchers compared death rates attributed to influenza over 31 years to absolute humidity readings nationwide; they also used a mathematical model of the influenza transmission cycle that incorporated previous findings of how absolute humidity affects the survival and transmission of the virus.  They reported that there were often significant drops in absolute humidity in the weeks prior to a flu outbreak.

Although noting that this dry period is not a requirement for triggering an influenza outbreak, they found it was present in 55-60% of the outbreaks analyzed.  The causal link?  The virus responded almost immediately to the dry period with the result that transmission and survival rates increase.  Further, about 10 days later, the observed influenza mortality rates occurred apparently as a result, at least in significant part.

The study can be found at http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1000316.

Scientists have long known that smokers and people exposed to secondhand smoke experience high rates of respiratory infections.  The presumption has been that smoking impairs lung function or immunity, which it may.  However, a more significant factor may be that cigarettes host hundreds of different bacteria, including those responsible for many human illnesses.

Researchers extracted tobacco particles sitting atop filters or inside cigarette packaging and placed the particles in a sterile culture medium that simulated human lungs.  In most cases, the researchers were able to grow bacteria that had been present on the near-microscopic flakes.  The most prevalent bacteria found to be present included Campylobacter, which can cause food poisoning; Clostridium, Corynebacterium, Klebsiella, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia - all of which are associated with pneumonia and other infections; E. coli; and, a number of Staphylococcus species that underlie serious hospital-associated infections.  The researchers note that it would be worthwhile to explore if the bacteria came from tobacco and were not merely reflective of environmental contamination.

The report can be found at http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.0901201.

Earlier research also sheds light on this subject.  Researchers found, without identifying specific species, that toxins produced by bacteria found in many filters (from tobacco particles embedded in the filters) caused damage to or destroyed red blood cells.

The report can be found at http://www.ncbi.nlm.nih.gov/pubmed/18768459.

Tobacco companies may be aware of this issue.  There is at least one patent that covers the use of an antibacterial wash on fresh or partially cured tobacco as a cost-effective method "of reducing both the numbers and activity of bacterial and fungal populations."  The patent points out that these microbes are responsible for producing endotoxins and tobacco-specific chemicals called nitrosamines.  Nitrosamines can cause cancer, and are a natural byproduct of the burning of tobacco.  It may also be that arise from microbial degradation of tobacco components.

The patent can be found at http://www.google.com/patents/about?id=foQQAAAAEBAJ&dq=6,755,200&as_drrb_ap=q&as_minm_ap=0&as_miny_ap=&as_maxm_ap=0&as_maxy_ap=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is.

Thus, issues of causation can often be much more complex and multifactorial than one would believe upon first impression.