Sorry to hear your husband has been suffering so much. Whil eit is possible that his symptoms are just the flu, that kind of joint-specific pain is not typical for the flu, plus it is a bit early for flu season (though not impossible).
To me, his symptoms sound very much like Lyme disease - the sudden onset, fatigue, fever, chills, severe joint pain, dizziness, and headache are all very common Lyme symptoms. The only symptom that doesn't fit is the cough. Lyme is now present in all 50 states(well, I'm not entirely sure about Hawaii!) and on every continent except Antarctica. It is almost at epidemic proportions in many places, including the northeast, mid-Atlantic, and midwest states. It is a very serious illness that must be treated promptly and aggressively. If left untreated or not treated thoroughly, permanent neurological damage can result. Anyone can get Lyme - many people get it just from being in their own yard - and the characteristic bulls-eye rash only occurs in about 50% of the cases (he should check his entire body, including hidden areas like the scalp and pubic area, for any kind of rash).
He definitely needs to see a doctor as soon as possible. Even if the doctor can find an explanation for the cough and fever (like bronchitis), the severe and sudden joint pain needs to be investigated. Even if he suddenly starts to feel better, he should not ignore this. Sometimes Lyme symptoms hit hard the first week or two and then fade away for a while. The longer Lyme is left untreated, the harder it is to get rid of.
In addition to Lyme disease, there are about a half dozen other infections that are also passed along by ticks. Many doctors don't know to test for all of these. If the doctor diagnoses Lyme and treats it but another infection is undiagnosed and untreated, the Lyme won't be fully eradicated and the patient will get progressively worse. That's what happened to my son - he was treated for Lyme but never even tested for theother infections. Last year he was diagnosed with Lyme, babesia, and bartonella which were probably all there from years before and is very sick now (and being treated).
I have both CFS and Lyme. Here's a blog post I wrote summarizing the tick-borne infections:
So, you should ask the doctor to test him for all of these. For Lyme, he should get both the ELISA and Western Blot tests...though none of these tests are 100% accurate - false negatives are very common. So if all tests are negative and his symptoms persist, he may still have Lyme. Some doctors believe the only true test is to try Lyme antibiotics and see if there's any effect.
Good luck and please let me know if I can help further.