Sir:
The paper by Palacios et al. [1] reports that Streptococcus pneumoniae coinfection is correlated with the severity of A/H1N1 pandemic influenza based on studies of those infected during the recent outbreak in Argentina. S. pneumoniae infection was also the most cause of death among those infected with A/H1N1 pandemic influenza in the 1918-19 pandemic [2,3].

There is a growing body of literature reporting that vitamin D, through induction of cathelicidin and defensins, can reduce the risk of both bacterial [4-6] and viral [7,8] infections. Based on this knowledge, an ecological study of case fatality rates in 12 U.S. communities [3] was conducted using indices for solar ultraviolet-B (UVB) doses [9]. Since vitamin D had not yet been discovered, solar UVB was the primary source of vitamin D. Since the half life of vitamin D in the body is 4-8 weeks and the peak mortality rates occurred in late autumn, both summertime [10] and wintertime (latitude) indices were used. The summertime UVB doses explained 46% of the variance while wintertime doses explained 42%. The mechanisms proposed to explain the finding were that 1,25-dihydroxyvitamin D shifts cytokine production from T-helper 1 (Th1) proinflammatory cytokines to Th2 cytokines [11], and induction of cathelicidin and defensins to fight pneumonia bacteria. One effect of proinflammatory cytokines is to disrupt the epithelial lining of the lungs, making it easier for pneumonia to invade. That vitamin D reduces risk of pneumonia infection is supported by a recent paper that reported the study of invasive pneumococcal disease in Philadelphia for six years: After adjustment for seasonality, yearly increases in reporting, and temperature, weekly incidence was found to be associated with clear-sky UV index (IRR per unit increase in index: 0.70 [95% CI 0.54-0.91]) [12].

What do we know about the epidemiology of the pandemic (H1N1) 2009 virus? It has been reported that groups with greatly increased risk, up to 4-6 times that for others, are pregnant women [13], those with metabolic diseases such as diabetes and obesity [14], and Australian Aborigines [15]. All three groups are known to be vitamin D deficient. Thus, during the A/H1N1 pandemic influenza, there should be a public health advisory to increase serum 25(OH)D levels, probably to about 40 ng/mL (100 nmol/L) [16].

William B. Grant, Ph.D.
Sunlight, Nutrition, and Health Research Center (SUNARC)
P.O. Box 641603
San Francisco, CA 94164-1603, USA
www.sunarc.org
wbgrant@infionline.net

References
1. Palacios G, Hornig M, Cisterna D, Savji N, Bussetti AV, Kapoor V, Hui J, Tokarz R, Briese T, Baumeister E, Lipkin WI. Streptococcus pneumoniae coinfection is correlated with the severity of H1N1 pandemic influenza. PLoS One. 2009;4:e8540.

2. Brundage JF, Shanks GD. Deaths from bacterial pneumonia during 1918-19 influenza pandemic. Emerg Infect Dis. 2008;14:1193-9.

3. Britten RH. The incidence of epidemic influenza, 1918-19. Pub Health Rep. 1932;47:303-39.

4. Zasloff M. Fighting infections with vitamin D. Nat Med. 2006;12:388-90.

5. Adams JS, Hewison M. Unexpected actions of vitamin D: new perspectives on the regulation of innate and adaptive immunity. Nat Clin Pract Endocrinol Metab. 2008;4:80-90.

6. Liu PT, Modlin RL. Human macrophage host defense against Mycobacterium tuberculosis. Curr Opin Immunol. 2008;20:371-6.

7. Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB. Epidemic influenza and vitamin D. Epidemiol Infect. 2006;134:1129-40.

8. Cannell JJ, Zasloff M, Garland CF, Scragg R, Giovannucci E. On the epidemiology of influenza. Virol J. 2008;5:29.

9. Grant WB, Giovannucci D. The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918–1919 influenza pandemic in the United States. Dermato-Endocrinology 2009;1: 215-9.

10. Leffell DJ, Brash DE. Sunlight and skin cancer. Sci Am 1996;275:52-3, 56-9.
http://toms.gsfc.nasa.gov... (accessed 2009).

11. Ardizzone S, Cassinotti A, Trabattoni D, Manzionna G, Rainone V, et al. Immunomodulatory effects of 1,25-dihydroxyvitamin D3 on TH1/TH2 cytokines in inflammatory bowel disease: an in vitro study. Int J Immunopathol Pharmacol 2009;22:63-71.

12. White AN, Ng V, Spain CV, Johnson CC, Kinlin LM, et al. Let the sun shine in: effects of ultraviolet radiation on invasive pneumococcal disease risk in Philadelphia, Pennsylvania. BMC Infect Dis. 2009;9:196.

13. Jamieson DJ, Honein MA, Rasmussen SA, Williams JL, Swerdlow DL, et al. H1N1 2009 influenza virus infection during pregnancy in the USA. Lancet. 2009;374:451-8.

14. Vaillant L, La Ruche G, Tarantola A, Barboza P; epidemic intelligence team at InVS. Epidemiology of fatal cases associated with pandemic H1N1 influenza 2009. Euro Surveill. 2009;14. pii: 19309.

15. Foley M, McNeil DG, Jr., Swine flu’s risks increase for Australia’s Aborigines. New York Times, August 15, 2009. http://www.nytimes.com/20... (Accessed September 3, 2009).

16. Goldstein MR, Mascitelli L, Pezzetta F. Pandemic influenza A (H1N1): Mandatory vitamin D supplementation? Med Hypotheses. . [Epub ahead of print]