I would like to discuss something that I have been practicing for years and am undergoing at this moment. (Have not had a cold or flu in at least eight years).
This might be very helpful in both the prevention and the treatment of the seasonal flu and cold symptoms.

Now, all diseases are caused by the accumulation of toxins in the body, (though toxins are also produced on the physical level by the stored negative feelings and emotions. This fact has been often demonstrated by taking blood samples of patients who were affected by either negative or positive influences, with no other factors being involved in the tests). Any spiritual problems will also manifest themselves on the physical level as toxins.

What is usually termed as a "cold" is actually the body's attempt to rid itself of toxic matter, i.e. through the production of mucus, by raising of basal temperature and other ways.

Since we are living on an extremely polluted planet, even if we follow an all-organic diet, live in the country away from major industry, do not smoke or take drugs or medications of any kind, we are still exposed to many toxic substances. In order to prevent diseases, the body must be cleansed on a regular basis, otherwise, it will try to bring your attention to this issue by creating serious problems.

The following cleansing treatment is known as "The Master Cleanser Fast" , and while nothig is ever truly "new" under the sun, in more recent times, this fast has been widely publicized by its re-creator Stanley Burrows in his book "Healing for the Age of Enlightenment".
It has been used by many thousands of people with great success, including those with problems such as gastric ulcers, diabetes, sinus infections, hepatitis A and B, cancer, autoimmune diseases such as arthritis and lupus, and many other disorders.

I have used it myself several times, and have benefitted enormously. I feel that no matter what shape you are in, it is very important to do a cleanse periodically. The menstrual period is one of the body's ways of cleansing itself, however, it is not usually sufficient these days.

Here is the recipe:

Two tablespoons lemon or lime juice (use organic fruit only, even if you use supermarket-bought fruit at other times)
Two tablespoons genuine maple syrup (use high quality maple syrup only, the kind you would find in a health-food store, grade C from Vermont or Quebec is best for your purposes. Do not use the maple-flavored corn or sugar-cane syrup you'd find in the supermarket).
1/10 teaspoon cayenne pepper or to taste.
10 oz spring or filtered water, medium hot, or warm.
If your goal is also to lose weight, you can reduce the amount of maple syrup slightly.
Drink up to twelve glasses of this mixture per day. (More, if you can handle it).

Do not consume any food while doing this fast. You may have as much water as you want, herbal teas are recommended. If you are habitually constipated, use laxative teas in tandem with the fast:
senna, cascara sagrada, wormwood, dandelion root, chickweed leaves and parsley, (also a wonderful liver cleanser, supports the kidneys).
This fast is usually recommended for 10 days, more if you feel up to it. Is has been done for as long as 150 days consecutively, but I do not recommend it, unless you are severely overweight.

Generally speaking, listen to your body, if you feel uncomfortable after a period of three to four days, you can stop. The first three days are the hardest, since most of the toxins leave your body during this period. You might get a slight headache and dizziness. These are just signs that toxins are being released into your bloodstream. The mixture contains all of the necessary minerals, carbohydrates and vitamins for your body to function normally, unlike a water-fast which is very hard on the body, and can cause some unpleasant side-effects.
You will lose the toxins first, the fat will follow. The muscle tissues are not affected. You might find that you have the urge to move your bowels several times daily, especially during the first three days. This is the sign that your body is cleansing itself.
People who are overweight will lose some excess fat on this fast, those who are at their ideal weight will not find any changes, and those who are underweight have been actually known to gain some weight as the result of the fast, odd as may sound.
The main objective here is to help your body heal.

Blessed Be!