Influenza
Friday, January 4th, 2008‘Tis the season for visiting and celebrating, but not all the visits will be welcome. Influenza is in season so it’s a good time to share what we know about this ancient scourge.
“Flu” is one of the most overused words in our language, invoked to describe every ailment we suffer, many not even respiratory. Personally I prefer the French name (la grippe) or Spanish (la grippa) because they are so descriptive, whereas “influenza” harks back to medieval notions of miasmas and evil spirits.
Comparing classic influenza to everyday colds and upsets is like comparing a crocodile to a gecko.
In my two years as a CDC epidemiologist my major areas of responsibility were influenza and hepatitis, and while based in Berkeley I was responsible for tracking these viruses and others and reporting to CDC. You could say I was lucky in that both years were epidemic ones in California, one A2 and one B. These are two of the three major types of human influenza, the other being A. Type B tends to be milder but has nasty muscle pain, whereas A and A2 feature sudden onset of high fever, dry cough, sore throat, headache but rarely vomiting or diarrhea. School absenteeism, typically 8-10%, jumps to 40% and may force closure. Nothing else but natural disasters has that degree of impact on schools. The other main indicator is excess deaths from respiratory illness. Influenza typically lingers for at least 5 days and attacks whole families and workplaces. Few adult illnesses involve 104 fevers except this one. Deaths occur in older populations and the chronically ill, but in recent years more fatalities have been recognized in infants. This could represent the availability of quicker bedside testing.
There are hundreds of books about influenza but mysteries remain. The pandemic following World War I killed as many as 100,000,000 people, but its classification is uncertain. Because a species of bacterium was isolated from many severe cases, it was named Hemophilus (“blood-lover”) influenzae, a misnomer that is still with us. Viruses had long been postulated but were still the stuff of science fiction until after WWII. Major epidemics occurred in the 50′s and 60′s and were usually referred to by Asian names because it became clear that new strains arose in China and made their way around the world, necessitating new versions of vaccines every year. Birds and swine are involved in the propagation of influenza, as is occurring now with the still nascent avian flu popping up around the world, mostly involving occupational exposure to infected domestic birds. For these avian strains to adapt to humans and cause serious epidemics requires several steps called mutations; the hope is that while adapting to humans the H5N1 virus, as it is called, will lose its virulence, but that is not certain. Remembering the swine flu fiasco of 1976, CDC is preparing for this new threat but keeping a lid on the hysteria that could erupt.
Influenza vaccination has been around for years and there is little resistance to using it yearly for the elderly, chronically ill, health care workers, the military, and other select groups. In children its use is more controversial. There is general agreement that infection with the current A, A2 or B strain will leave the patient immune to that strain for many years, perhaps for life, and that healthy young individuals will recover. Giving the vaccine to children is more of a public health strategy in that it may help control the spread of the virus in the community, but the benefit to the individual child is limited to perhaps 80% protection for one year. It is untrue that people can “get the flu” from the shot; it is not a live virus. Be that as it may, a fair percentage of parents are refusing the vaccine, and as long as the children are healthy I’m OK with that. There are certainly much higher priorities in vaccination with greater benefit. There is now a live intranasal vaccine but its expense and other concerns have limited its use.
Treatment is not much different than it was in 1918. There are prescription drugs that cut a day or so from the illness but they are not tolerated by children. Antibiotics are not helpful unless secondary infection develops. Hydration and rest are essential. Fever and other symptoms can be treated as necessary. Although a classic case is unmistakable (“How fast was that bus going when it hit me?”) there are many folks who become infected and don’t even know it. Studies have been done in large workplaces, taking blood samples throughout an epidemic period, and the most significant factor correlating with absenteeism was the emotional state of the individual at the start of the study.
One of the great unsolved mysteries of this disease is where the virus goes when spring arrives. It is common for an outbreak to stop in March and resume in the same community in November, having disappeared all that time. In our area we haven’t had a major outbreak in almost 40 years. I suspect that our patchwork school calendar may have something to do with that, since some kids are off during the high-risk months. Perhaps I shouldn’t have said that – might arouse those medieval spirits.