The cause of Th2 to Th1 imbalance in asthma: A function of exposure to typhoid and tuberculosis?

[Extract]
The prevalence of asthma varies from country to country, from a low of 2% to a high of 30% (1). The reasons for this extreme variation in asthma prevalence are unclear. Investigation of exposure to environmental triggers such as allergens and air pollution (2) yields inconsistent and confusing results. Paradoxically, in Mexico and Eastern Europe, which have an increased level of air pollution, the prevalence of asthma is very low. However, in the South Island of New Zealand, the air quality is good and asthma prevalence is very high. In this article, we will review some current concepts in asthma and use global epidemiologic information available through the World Health (WHO) to propose a theory to explain these phenomena.