住房拥挤、卫生条件差和免疫系统受损无论因为营养不良还是HIV等慢性感染，均为传染病的蔓延提供了肥沃的土壤。
Crowded housing, poor sanitation, and compromised immune systems, whether owing to malnutrition or chronic infections such as HIV, provide fertile ground for contagion.