I had been feeling tired for about 36 hours. Then came the sore throat, followed by a dry cough. By Saturday the sweating and shivering had started and I returned to bed, with a thumping headache and muscle aches all over. Bank holiday weekend plans were abandoned. Trips to the bathroom brought on dizziness. Bouts of spontaneous sweating followed periods of intense cold and shivering. And when I finally surfaced on Sunday, the "rubbery" feeling in my legs were a strong signal not to attempt any serious exertion.
The cough became productive, to be joined by a wheeze and chest tightness. On the plus side, I had no running eyes or nose and my gastric system remained unaffected. So, was I an unseasonably late victim of influenza? Or was this an infection by a different virus, or even a bad dose of the common cold?
The lack of coryzal symptoms (runny nose and sneezing) and the fact that I had a fever made it easy to rule out the common cold. Caused by a wide range of viruses, each with multiple strains, adults get a cold two to three times a year. Usually self limiting, most of us will treat ourselves for the symptoms; only half of one per cent will go on to develop a secondary bacterial infection of the sinuses which will require antibiotic treatment.
The severity of the symptoms certainly made a full-blown influenza attack possible. Both influenza A and B were circulating this winter, without causing the near epidemic levels of illness seen in the winter of 1999/2000. But in May?
Sporadic summertime influenza infections are not unknown, but they are not a common occurrence. In making a diagnosis of "full-blown flu" a doctor will be influenced by the knowledge that strains of influenza virus are in circulation. This information is now available in the Republic by means of a sentinel practice network run by the Irish College of General Practitioners and the National Disease Surveillance Centre which formulate regular reports based on specialised swabs sent by GPs to the Virus Reference Laboratory.
These swabs are not routinely used in clinical practice, so the diagnosis of influenza remains a clinical, or non-laboratory one. The criteria include a fever of 37.8 degrees Celsius or greater and/or feverishness (shivers, hot and cold sweats). In addition, there must be two of the following symptoms: cough, sore throat, muscle pains and headache.
Based on this, my putative influenza diagnosis still stands up. However, the onset of symptoms - if the tiredness is included - were not abrupt, something that is quite typical of a full-blown flu. Patients will classically describe being at full tilt one minute and, literally, falling over an hour later.
Another symptom I ask about, is the person's ability to lift their head off the pillow. In a true influenza attack, they are bed-bound and not inclined to move no matter what pressing engagements await.
Based on these latter criteria, my diagnosis looked less certain, although the length of symptoms at five to seven days was about right.
Regardless of whether it is true influenza or a bad dose of another type of virus, why are we bothered about making an exact diagnosis? Is the treatment - bed rest, clear fluids, paracetemol and nasal decongestants - not the same anyway?
The reason for the diagnostic drive is the influenza viruses' ability to cause significant complications, especially in the very young and the elderly. Pneumonia is the commonest complication; either a primary viral or secondary bacterial pneumonia, which can be fatal. A study has found that one in 50 elderly people required admission for heart failure brought on by the flu. Pre-existing asthma and chronic bronchitis will also be worsened by viral infection. The heart muscle can also be inflamed by influenza, as can the brain, although neither is usually fatal. Young adults with influenza A infection can sometimes develop kidney failure.
Another reason for seeking an accurate diagnosis is the availability of treatment for "true flu". A drug called Zanamivir, delivered by inhaler, has been shown to reduce the length of symptoms if given early in the illness.
In the best traditions of "physician diagnose thy self", my considered opinion is that I did not have influenza infection. But whatever viral infection I had produced a nasty illness.
And although I would like to encourage the use of the term "viral illness" rather than the loose bandying about of "the flu", I have to admit that the latter is a more powerful message for most of us ringing in sick to work. Any takers for the halfway house of "flu-like illness"?
Dr Muiris Houston, Medical Correspondent, can be contacted at mhouston@irish-times.ie or leave messages on tel 01-6707711, ext 8511, but he regrets he cannot reply to individual medical problems.