Low White Blood Cell Count (3.8) -- 30 year old male

[Jhunt223]

Just found out I have a low blood cell count (3.8) after having routine blood work done. I'm an otherwise healthy 30 year old male. I exercise regularly and a reasonably well rounded diet. My work does require me to pull long hours and be away from home for extended periods of time, which I think contributes to a lack of sleep. I probably average 5-6 hours of sleep nightly.

I was involved in a high risk sexual encounter about one and a half years ago which led me to take HIV medication for a month just to help prevent infection in the event I had indeed been exposed. I was subsequently cleared through testing. There's a nagging voice in the back of my head suggesting that perhaps those results were erroneous right now.

I see "viral infections" listed as a potential cause of low wbc across the internet. Would the common cold or flu fall under this category or does this apply to more severe infections?

Thanks in advance for any help or opinions.