If you're concerned about factors associated with mental illness, you don't need to worry about

a hereditary
b virus infections
c physical factors
d early expierences

Each of the factors listed can have an impact on mental illness depending on the context and the specific illness in question. However, if the question suggests which factor you might be least concerned about, it would typically be:

b. virus infections

Explanation for each factor:
a. Hereditary - Genetics can play a significant role in the predisposition to various mental illnesses. Family history of mental disorders can be a risk factor.

b. Virus infections - While certain virus infections have been associated with the development of specific mental health issues, they are generally less commonly implicated in the development of mental illness than genetic, environmental, early experiences, or physical health factors.

c. Physical factors - Physical factors such as brain injury, hormonal imbalances, or exposure to toxins can contribute to mental health disorders.

d. Early experiences - Adverse early life experiences such as trauma, abuse, neglect, or stress can have long-lasting impacts on mental health.

When considering mental illness, it is essential to understand that it is often the result of a combination of factors, including but not limited to genetics, brain chemistry, life experiences, and environmental influences. Individuals concerned about mental health should seek professional advice for personal risk assessment and possible preventive measures.