Int. J. Environ. Res. Public Health 2010, 7 939 Abbreviations: EM—electromagnetic; EMF—electromagnetic fields; ELF EMF— extremely low frequency EMF; CRY—Cryptochromes; CBP—CREB binding protein 1. Introduction Influenza pandemics have been threatening to people for many centuries. Each influenza pandemics bring on huge financial and people losses. Timely and correct epidemiological prognosis could attenuate the damage. But it is not an easy task, because numerous factors influence the occurrence of influenza (like any other) epidemics, among them:  virus evolution dynamics;  host’s sensitivity;  conditions for viral transmission, etc. Therefore, it is always difficult (if possible at all) to make an exact epidemiological forecast. However, reliability of any prognosis increases with an increase in our understanding of underlying mechanisms and influencing factors. There is an opinion that solar activity can impact epidemic processes. Chronology of influenza pandemics in 20th century (1946–1947, 1957 and 1968) suggested existence of 11-years periodicity in flu pandemics. At the same time, cycles of solar activity usually have 11-years periodicity as well. Could it be just a simple coincidence? In the beginning of 20th century, Russian scientist A. Chizhevsky suggested correlation of some biological processes on the Earth with cycles of solar activity [1]. But possible mechanisms of such interrelation are still not completely understood. In this paper, we support an idea of a definite role of electromagnetic and Geomagnetic fields in biological regulation, including regulation of gene expression patterns in any living being that can directly influence flu epidemic process and any other biological phenomena. Existence of “electromagnetic bio-regulation” would easily explain solar influences on the Biosphere. We’re going to expound our views and pertinent data in the literature in the following order: (a) To bring attention to periodicity as a common feature of numerous biological processes and to discuss the nature of corresponding regulatory influences; (b) To show theoretical possibility of bio-regulatory effects of magnetic fields; (c) To outline some signaling pathways capable of implementing bio-regulatory (including genome-regulatory) functions of electromagnetic fields; (d) To summarize our knowledge about Geomagnetic field, its principle parameters and sources of variation; (e) To review possible evidences of regulatory influence of Solar cycles and corresponding Geomagnetic field perturbations on flu epidemic process; (f) To describe probable mechanisms of Solar cycles and Geomagnetic field regulatory influences on virus-host interactions and other biological processes.