What is the fine-grained topic of the following text: For example, infants whose immune system has not fully developed, people who are too old to have a strong immune system, and those suffering from chronic diseases such as AIDS, cancer, pneumonia, bronchitis, and other respiratory ailments, are the ones who are severely and the most affected by the exposure to toxic black mold. Only return the topic.
Effects of toxic black mold on individuals with weaker immune systems