Chinese avian influenzaBMJ 1998; 316 doi: https://doi.org/10.1136/bmj.316.7128.325 (Published 31 January 1998) Cite this as: BMJ 1998;316:325
The H5N1 virus will probably not result in a pandemic
Influenza viruses are unique among respiratory viruses in exhibiting “drift,” which is change in surface antigens as a result of host immunological pressure. In addition, influenza A viruses exhibit “shift”—which is the genetic intermingling of human strains with animal or bird strains, resulting in completely new viruses of pandemic potential. This makes the production of long lasting comprehensive vaccines impossible and continual monitoring for the appearance of new strains essential. Moreover, unlike infections transmitted through blood, food, or water, those transmitted through the respiratory tract are difficult to control through public health measures apart from vaccination and in controlled situations such as laboratories or under barrier protection conditions. Hence the current interest in so called Chinese or Hong Kong flu.1 International travel adds an extra urgency to this problem because of the speed with which a new virulent strain could potentially spread worldwide.
The most dramatic example in the past of a devastating influenza pandemic was in 1918, when tens of millions died worldwide from so called swine flu (influenza A type H1N1). Smaller pandemics have occurred since, in 1957 and 1968, but each year there is speculation about whether or not we are on the verge of another major global outbreak resulting from further shift.
The influenza A strain involved in the latest outbreak in Hong Kong (H5N1) is not new. It was first isolated in South Africa in the 1960s and has since caused epidemics in poultry. However, in the spring of 1997 it caused the deaths of many thousands of chickens in Hong Kong, and increasingly intensive surveillance was started after a human case was recognised in June 1997.
Until 26 January 1998 there had been 18 confirmed cases with six deaths reported to the World Health Organisation, with no new cases reported after 17 January. All are confined to Hong Kong. The first of these deaths was from the complication of Reyes' syndrome, not directly from the virus infection itself. To date no convincing evidence exists of human to human spread, and most cases had been previously exposed to poultry. Unless human to human spread occurs neither a local or global epidemic is expected.
With intense international interest and the help of the WHO, surveillance continues in Hong Kong both in hospitals and in the community. Support is being given to the authorities in mainland China to determine whether there is evidence of infection there. Also all poultry in Hong Kong have been destroyed as a precautionary measure.
While there are no immediate plans by the WHO to advise the manufacture of a new vaccine that would cover the H5N1 strain, “seeds” are being developed for such a contingency. It has been suggested that the antiviral agent amantidine, which has been shown to be active against H5N1, could be used early in any suspected or possible cases. The WHO sees no reason to restrict travel to Hong Kong.
To consider the possibility that H5N1 or other new pandemic strains might be imported into Britain the departments of health have recently drawn up influenza pandemic plans for the United Kingdom. National and local working groups have been established to ensure that in the event of a British epidemic the impact on the health of the population and on the healthcare system is minimised. Even if, as seems likely, the H5N1 virus fails for the time being to result in a pandemic this exercise will have provided valuable experience and preparation for any future pandemics.