Clean Sweep for HK-68

Hong Kong flu has now made a virtual clean sweep of the U.S. At its worst, it reached epidemic proportions in 39 states, according to the National Communicable Disease Center in Atlanta. Ten other states reported more localized outbreaks. Only in Louisiana have there been too few individual cases to warrant the term epidemic.

In any influenza outbreak, the symptoms vary widely. Some specialists in epidemics and infectious diseases are convinced that the virus labeled A2-Hong Kong-68 is proving more variable than most preceding strains. For one thing, many victims describe symptoms that seem conspicuously different from those of the patient next door. One man may suffer a three-day bout of sniffling, coughing, headache and muscle twinges, with little fever, while his neighbor may run a high fever, return to work after a miserable week in bed, and promptly suffer a disabling relapse.

Quick-Change Artists. Why does one man get off lightly, while another is hit so hard? The explanation may lie in both the nature of the virus and the patient's previous bouts with flu. The first A2 Asian virus appeared in 1957 and laid low millions around the world. Thanks to antibody formation, these people developed substantial immunity against further illness from this virus or its kin. But flu microbes, almost unique among the 500 or more viruses that plague man, are capable of quickly altering their antigenic properties. Thus they require different antibodies to neutralize them. HK-68 certainly represents a major mutation from the A2 of 1957-58. Whether it is different enough to rate a new designation as A3 is still questionable.*

Nevertheless, the limited similarities between older A2 strains and HK-68 account for the sharp differences in symptoms among victims, according to the University of Illinois' Dr. Robert L. Muldoon. A severe bout of A2 years earlier left some persons' systems ready to react instantly and forcibly against any related virus. Many of this winter's flu victims had never had Asian flu, and therefore had no foundation antibody on which to build a counterattack.

Camel back Effect. As a result, many physicians believe that HK-68 is especially threatening to young, healthy adults. In most epidemics, only the aged, the infirm or the ailing young develop pneumonia as a result of direct infection of the lungs with flu virus. Others may develop a "secondary" bacterial pneumonia because their systems have been weakened by flu. By contrast, this winter more young men and women have gone rapidly from influenza to influenzal pneumonia. Some victims get out of bed after about with the flu only to be hit by a second round. According to Dr. H. Bruce Dull, the NCDC's assistant director, most of the fault for this two-peak "camelback effect" lies in patients' impatience.

The latest bulletins from the NCDC report that the epidemic has passed its peak. But for disrupted organizations and miserable individuals, statistics are slim comfort. The new flu will still sicken thousands of Americans before it fades away.

* Two categories of flu virus appear most often in the U.S.A and B. The A strains seem to mutate more rapidly, causing epidemics. A1 appeared in the U.S. in 1947.

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