Virus Mixing Cited As Possible Cause Of Flu Epidemics
"...not only did Flu A originate from birds, but every year the epidemiologists can trace the virus recombination in migrating birds from HK to Australia and back. Allowing a guess as to what the next yr's variety will look like."
Another feeling new for me from you. A tidbit regarding migrating birds this time. It led to this from my childhood town. Vancouver was smaller in '45.
By Walter Sullivan Special to The New York Times
Aug. 23, 1975
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VANCOUVER, B.C., Aug. 22 —Recent laboratory experiments have lent support to the theory that global epidemics of influenza occur after an entirely new flu virus is created by the natural recombining of fragments of virus strains from human beings, other mammals and birds.
In the experiments, described at the Pacific Science Conference, held here this week, new infectious viruses were created, and the research was carried out under intensive quarantine to prevent their escape, possibly setting off an epidemic. In one case the creation of a virus produced a “mini-epidemic” among laboratory animals.
While the results of the research, conducted on Plum Island, at the eastern end of Long Island Sound, are compatible with the virus recombination hypothesis, it was stressed that the concept had not yet been proved.
If the recombination hypothesis is correct and such a new virus could be identified before it strikes humanity, it might bet possible to develop c vaccine in time to stem an incipient global epidemic, or pandemic.
Another pandemic has been forecast for the 1978-80 period.
A worldwide effort is therefore under way to capture and freeze as many types of flu virus as possible to see whether the manner in which the pandemic virus emerges can be traced. Progress in this effort has been reported by participants in the meeting herte, at the University of British Columbia.
Flu pandemics strike the world at intervals of 10 to 15 years, killing many thousands and bringing misery to millions.
At the congress this week, scientists from Australia, Britain, Japan, New Zealand, the Soviet Union and the United States reported finding a wide variety of flu viruses in Arctic seals, Ukrainian ducks, Kamchatka chickens, Azerbaijan cattle, Vladivostok spaniels, Hong Kong pigs, turkeys in the Central United States and various other fowl.
Often the bearers of these viruses show no symptoms because they are equipped with chemical defenders, or antibodies. Insofar as some of these strains also infect people, they, too, have developed general immunity. Some still come down with flu because the virus tends to change in minor ways—a process known as “drift.” The effect is catastrophic only when a completely new strain appears.
According to the recombination hypothesis, recombination would form something entirely new against which existing antibodies would be useless.
The research facility on Plum Island, known as the Plum Island Animal Diseases Laboratory, is run by the United States Department of Agricutulre.
The experiments on recombinations were done chiefly on Plum Island because it is closed to the public and the laboratory there, like one engaged in biological warfare research, is equipped to prevent the escape of newly created virus strains that might cause an epidemic.
Such research, however, falls into a category that has recently become subject to searching review and regulation to minimize the risks.
The experiments were described by Dr. Robert G. Webster of St. Jude's Children's Research Hospital in Memphis, who leans toward the recombination concept.
“An increasing body of evidence,” he reported, “indicates that the completely new viruses responsible for pandemics do not arise by evolutionary change, or mutation, of existing human strains.”
Experiments With Animals
The experiments on Plum Island have shown, he said, that flu viruses from man, lower animals and birds can recombine in live animals. He emphasized that this does not demonstrate that such recombination under natural conditions is responsible for pandemics.
In one experiment, one pig in a herd was infected with the human type of virus responsible for the 1968 pandemic of “Hong Kong” flu and another pig was infected with a pig influenza virus. Within a week, pigs in the herd carried a hybrid of the two viruses, as well as the original strain.
In a similar experiment with turkeys, one was infected with fowl plague virus and another with turkey influenza virus. The resulting recombination produced a “mini epidemic” among the turkeys.
But, Dr. Webster asked, if recombinations come so easily, why are there, not more pandemics?
To prove the recombination hypothesis, he said, the virus responsible for a pandemic must be found beforehand in birds or mammals. “This is the direction we are taking at the moment,” he added.
The agency responsible for keeping track of worldwide flu virus trends is the World Influenza Center in London. Dr. Geoffrey C. Schild of the center reported to the meeting present concepts concerning the variable structure of that virus.
There are four parts, he said, that can stimulate the body's defenses. Two (the nucleoprotein and a matrix protein) are internal and occur only in two unchanging forms. These determine whether the virus is one of two basic types, designated A and B.
The other two are external and highly variable. They are defined chemically as a hemagglutinin and a neuraminidase. A virus produced by recombination might carry one such external structure of human origin and the other of animal origin.
Hong Kong Flu Theory
Dr. W. G. Laver of the John Curtin School of Medical Research in Canberra, Australia, believes that Hong Kong's flu was caused by a virus that combined the neuraminidase from the human virus with a hemagglutinin of animal origin. Similar combinatiods destined to cause future pandemics may already be circulating among far ranging sea birds of the Pacific, he said.
He cited as one candidate a new strain isolated by his laboratory from a single shearwater nesting on an uninhabited coral island on the Great Barrier Reef off Australia.
Because most if not all pandemics seem to originate in Southeast Asia, some have thought that pigs, widely raised and eaten there, might be the reservoir within which recombination occurs. For this reason, a group of public health specialists visiting China recently had hoped to bring home extensive samples of swine blood serum from South China, but were able to obtain only a single specimen.
The Soviet findings were reported by Dr. Dimitri K. Lvov on behalf of himself and a number of colleagues from the Ivanosky Institute of Virology in Moscow and the Institutes of Epidemiology and Microbiology in Khabarovsk and Vladivostock. Research on the problem was initiated in 1970, he said, producing extensive evidence that a flu virus infecting one species, notably man, can be transferred to other species such as birds, seals and dogs.
It has not been possible so far to learn to what extent, if, any, flu viruses are transmitted from animals to man. The disease typically is spread via the respiratory system.
INSERT: It seem 45 years later not much more has been gained on that specific 'animals to man' question. Transmission of Avian Influenza A Viruses Between Animals and People [... to end .. ] Although it is unusual for people to get influenza virus infections directly from animals, sporadic human infections and outbreaks caused by certain avian influenza A viruses and swine influenza A viruses have been reported. https://www.cdc.gov/flu/avianflu/virus-transmission.htm]
High Variability Found
During an outbreak of Hong Kong flu in Vladisvostock in 1970-71 it was found that the “identical” virus infecting human beings occurred in local spaniels. Blood specimens from 1,606 cattle in various parts of the Soviet Union showed high variability and evidence for current or past flu infection. In some herds none was found. In others, the rate was 82 per cent.
An expedition to the fur seal colonies of the Commodore Islands—the Soviet continuation of the Aleutian chain—sampled blood from several hundred seals. In one group, 29 per cent had been infected with some form of Hong Kong flu. Some of the samples were sent tc Dr. Schild in London for further analysis.
In Kamchatka, white leghorn chickens were infected with human strain causing a small epizootic (the animal counterpart of an epidemic). Similar results were obtained with gulls. The virus occurs in many forms; in 3,300 birds collected from a wide range of sites, 122 strains were found. The birds included gulls, herons, ducks, terns, frigate birds, cormorants and snipes.
Some marine birds, Dr. Lvov noted, nest close to seal colonies and could therefore act as virus carriers. They also migrate between the Northern and Southern hemispheres. Thus, some suspect the original spread of a new virus could be through birds rather than human beings traveling between hemispheres.
Dr. Jar Miles of the University of Otago in New Zealand noted that spread of the most recent strain of human flu must, in some manner, have been airborne. It is known as the Port Chalmers strain as it caused a mild epidethic in that New Zealand port late in 1973.
However, the strain first appeared in human beings 10 days earlier in western Australia 4,000 miles to the west. Within a year, according to Soviet reports, a similar strain was evident in Russian chickens. Dr. Miles cited Malaysia as, perhaps, the original source.
Dr. Bernard C. Easterday of the University of Wisconsin, lust back from bird collecting in the Pribilof Islands of the Bering Sea and Northern Alaska, said that, despite all the new evidence, “the precise role of free-flying birds and domestic fowl remains obscure.”
While it is evident that virus strains pass back and forth between species, he said, “we don't know which animal is doing what to whom.”
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