Does Sunlight Regulate Avian Influenza (Bird Flu)?

Forrest M. Mims III

In 1995 NASA's Goddard Space Flight Center (GSFC) sent me to Cuiaba, Brazil, to measure the ozone layer during the peak of the annual burning season. The measurements were a part of the SCAR-B project. The total ozone measurements made from Cuiba showed a diurnal increase, with higher ozone building each afternoon due to the ozone precursor gases in the thick smoke. More interesting was the fact that solar ultraviolet was severely diminished by the severe air pollution. I suggested to my student assistant, Damian Kilday, and some NASA scientists that the suppressed ultraviolet might allow pathogenic bacteria, which are ordinarily killed by solar UV-B, to proliferate. Thus, the respiratory illnesses that affect many Brazilians during their burning season might be due in part to increased numbers of pathogenic microbes suspended in the air.

The 1995 trip to Brazil was described informally in three columns in The Citizen Scientist (see Part 1 , 2 and 3 ). The scientific findings from the research led to several talks and publications. In 1997, I returned to Brazil on behalf of the University of Sao Paulo and GSFC. The principle purpose of the visit was to measure total ozone, optical depth, solar UV-B, photosynthetic radiation and temperature at Alta Floresta, a remote town in the southern Amazon basin. In addition to many instruments, my student, Brad White, and I brought along a portable garden for growing various plants and some 60 sterile agar trays for sampling airborne bacteria.

Brad and I spent a busy three weeks making thousands of atmospheric measurements and sampling bacteria at the same time that UV-B was measured. Each day we had time only for a very brief breakfast and no lunch. So we thoroughly enjoyed our supper each evening. We then spent the evening washing clothes in a sink, filtering the next days supply of drinking water, backing up data and photographing bacteria colonies. The 1997 trip to Brazil was described informally in four columns in The Citizen Scientist (see Part 1 , 2, 3 and 4).

We found a significant association of changes in population of nonpigmented airborne bacteria and UV-B suppressed by smoke (see publication reprinted below). This suggested that my 1995 hypothesis about respiratory disease might be correct. Before leaving Alta Floresta, I received permission from the local health authorities to hire a student, Gisele Cristina de Castro, to survey the incidence of various diseases at Alta Floresta. Ms. Castro's findings showed a clear increase in influenza during the burning season on 1997. When avian influenza outbreaks began occurring in Southeast Asia, I checked the Navy's aerosol forecasts and found that outbreaks during January through March were associated with significant air pollution caused by biomass smoke. Thick cloud cover can also block solar UV-B, and GSFC's Tom Eck reminded me that the rainy season precedes the Southeast Asia burning season. Bird flu was also associated with the rainy season.

Science and Nature are the world's leading scientific journals and both have published letters that I wrote suggesting possible connections between suppressed UV-B and increased infectious disease. Therefore, on 15 March 2005 I sent to Nature a presubmission inquiry proposing a full paper on the UV-B-bird flu hypothesis. Within only hours, Dr. Rory Howlett, Nature's Deputy Biological Sciences Editor, politely rejected the proposal. He wrote (in part), "We are not persuaded that the firm conclusions that can be drawn from this current work will have a sufficiently immediate impact on our broader readership to justify publication in Nature rather than a more specialist journal."

During the summer I worked on a formal paper that describes in detail the suppression of UV-B by biomass smoke and the airborne bacteria and influenza findings from Brazil. This is a difficult paper, and there was very little spare time available Because the bird flu season was fast approaching, I decided to expand the publication inquiry to Nature into a letter to Science. The letter was sent on 18 August 2005 and rejected anonymously and without explanation on 22 August.

Nature and Science publish only 5 to 10 percent of articles they receive. Therefore, I decided to try a more hospitable journal, Environmental Health Perspectives (EHP). The letter rejected by Science was slightly revised and sent to EHP on 25 August 2005. It was accepted on 2 September 2005 and published in the December 2005 issue of the journal. EHP is published by the National Institutes of Health online and in hard copy. The journal is not copyrighted, so anyone with web access can read it.

The bird flu letter follows. I hope to find time to complete the formal paper before the 2006-07 bird flu season.

Avian Influenza and UV-B Blocked by Biomass Smoke

[citation in pubmed]

Washam (2005) described various poultry inoculation strategies being considered for controlling the spread of avian influenza in Southeast Asia and China. Longini et al. (2005) proposed that a future avian influenza A pandemic might be contained at the source by targeted prophylaxis, quarantine, and prevaccination.

Washam (2005) correctly noted that "Asian farmers, though, are running out of options." I propose a new option: Avian influenza might be controlled by a substantial reduction in regional scale biomass smoke in Southeast Asia that will allow natural solar ultraviolet-B radiation (UV-B) to suppress the virus before infection occurs.

Influenza viruses and various nonpigmented bacteria are killed by UV-B wavelengths in sunlight (Hollaender and Oliphant 1944). Biomass smoke significantly suppresses natural levels of UV-B, and severe smoke pollution reduced UV-B by up to 95% during the burning seasons in Brazil in 1995 (Mims 1996) and 1997 (Mims FM III, White B, unpublished data). Reduced UV-B on 6 days in August 1997 was well correlated ( r² = 0.83) with an increase in the ratio of nonpigmented bacteria vulnerable to UV-B to pigmented bacteria that are protected from UV-B (Mims and White 1998). Although airborne influenza viruses were not measured, 1997 hospital admission records at Alta Floresta, Brazil, showed that influenza incidence was highest during the burning season (de Castro GC, personal communication).

Human cases of avian influenza in Thailand and Vietnam peaked during the winter burning seasons of 2003 and 2004 (Thailand Ministry of Public Health 2005). Assuming similar optical properties of biomass smoke in Southeast Asia and Brazil, where UV-B and optical depth are highly correlated, optical depth measurements over Thailand and Vietnam by NASA's Terra and Aqua satellites suggest highly suppressed UV-B during these avian influenza outbreaks (Mims FM III, unpublished data).

Human cases of avian influenza in Thailand and Vietnam since December 2003 have peaked during both the rainy season and the burning season. Thus, periods of prolonged cloudiness and severe smoke pollution could play a role in initiating avian and other influenza outbreaks by attenuating the solar UV-B that might otherwise suppress influenza viruses in outdoor air exposed to sunlight. The transmission of avian influenza to people during these periods is enhanced by the fact that poultry raised for human consumption are often kept within several meters of where people live (World Health Organization 2004).

The author declares he has no competing financial interests.

Forrest M. Mims III
Geronimo Creek Observatory
Seguin, Texas
E-mail: forrest.mims@ieee.org

References

Hollaender A, Oliphant J. 1944. The inactivating effect of monochromatic ultraviolet radiation on influenza virus. J Bacteriol 48:447-454.

Longini IM Jr, Nizam A, Xu S, Ungchusak K, Hanshaoworakul W, Cummings DAT, et al. 2005. Containing pandemic influenza at the source. Science 309:1083-1087.

Mims FM III. 1996. Significant reduction in UV-B caused by smoke from biomass burning in Brazil. Photochem Photobiol 64:123-125.

Thailand Ministry of Public Health. 2005. Avian Influenza Surveillance in Human as of July 1, 2005. Available: http://thaigcd.ddc.moph.go.th/AI_case_report_050701.html [accessed 25 August 2005].

Washam C. 2005. On hens and needles. Environ Health Perspect 113:A370.

World Health Organization. 2004. Avian Influenza A(H5) in Rural Areas in Asia: Food Safety Considerations. Available: http://www.who.int/foodsafety/micro/avian2/en/ [accessed 25 August 2005].