The prevention and treatment of viral respiratory disorders
A briefing from the Board of Science
September 2007
Pandemic infection
The word pandemic comes from the Greek (pan – all and demos – people) and is an epidemic (a widespread infectious disease that affects many individuals in a population) that occurs over a much larger area eg on an international, intercontinental or even a global scale.
‘An influenza pandemic occurs when a new influenza virus appears against which the human population has no immunity, resulting in several simultaneous epidemics worldwide with enormous numbers of deaths and illness. With the increase in global transport and communications, as well as urbanization and overcrowded conditions, epidemics due to the new influenza virus are likely to quickly take hold around the world.’ [see reference 16]
An outbreak of infection is defined as being of pandemic proportions primarily by how fast it spreads, rather than by what proportion of the population is affected. According to the WHO, a pandemic can startwhen three conditions have been met:
- the emergence of a disease new to the population
- the agent infects humans, causing serious illness
- the agent spreads easily and sustainably among humans. [see reference 29]
- Spanish flu – 1918-19 (H1N1 virus) it is estimated that in the first six months Spanish flu had killed 25 million people, with the total number estimated as between 50 and 100 million. [see reference 30] The virus disappeared after 18 months as quickly as it had began. It is estimated that 17 million died in India, 500,000 in the United States and 200,000 in the UK.
- Asian flu – 1957-58 (H2N2 virus) is estimated to have caused between one and two million deaths worldwide.
- Hong Kong flu – 1968-69 (H3N2 virus) is estimated to have caused approximately one million deaths worldwide. [see reference 31]
For further information about the WHO global influenza program please refer to www.who.int/csr/disease/influenza/en and WHO global influenza preparedness plan (2007). [see reference 32] Read more information about the BMA’s views on vaccine development for pandemic influenza.
Avoiding the spread of pandemic infection
Should there be a viral pandemic, such as a new strain of influenza or severe acute respiratory syndrome (SARS), it is likely that additional measures would need to be taken in order to reduce the risk of spread of such a virus. The WHO advise a number of measures including:
- wearing scarves or face masks
- staying at home as much as possible to reduce the risk of contact with the virus
- keeping at least one metre away from people
- travel restrictions. [see reference 33]
‘Avian influenza is caused by viruses occurring in birds, who usually do not get sick from them. There are numerous strains of the influenza virus, with all the H and N genotypes originating in migratory
waterfowl’. [see reference 34] The current concern is that the H5N1 strain may mutate into a strain capable of efficient human-to-human transmission, and cause a pandemic. This strain was first recognized in 1997 when it infected 18 people in Hong Kong and caused six deaths, and human cases of the virus have since been found in at least 10 countries worldwide. [see reference 35] More information about the outbreak of bird flu cases globally can be found at the WHO website.
‘Avian viruses in wild bird populations are transmitted to domestic birds or sometimes to pigs. New strains can evolve when animals are near each other (the process known as “recombining”). While humans have developed a degree of immunity to various influenza strains because of exposure over time, the H5 strain is new to humans, rendering us highly susceptible if it were to become widespread in the population. A human pandemic occurs only when a virus introduced into the human population through another species becomes transmissible from person to person. Research is underway into the development of vaccines against this virus strain, as well as into other methods of prevention.’ [see reference 35]
The WHO has announced that it is working with vaccine manufacturers to create a global stockpile of vaccine for the H5N1 avian influenza virus. [see reference 25] GlaxoSmithKline has announced that it will contribute to the H5N1 global vaccine stockpile, along with Omninvest, Baxter and Sanofi Pasteur. Further work is needed on detailed operational planning for the stockpile, including how and under which conditions it will be deployed, as well as regulatory aspects. ‘Other measures being taken by WHO to prepare for a potential influenza pandemic include:
- rapid containment plans to stop a pandemic using public health measures (isolation, quarantine of contacts, personal hygiene and social distancing) and antiviral drugs
- assistance to countries to increase vaccine production capacity, including research and promoting the transfer of technology to developing countries.’ [see reference 35]
The BMA recognises that influenza (commonly referred to as flu) can be a serious infectious disease, particularly among vulnerable at-risk groups. Influenza infections are capable of reaching pandemic
proportions; this could present a serious threat to human health and result in widespread social disruption. [see reference 36]
BMA policy is primarily on pandemic influenza and contingency funding. The BMA believe that the Department of Health (DH) should act on the recommendations of the House of Lords’ select committee on pandemic influenza, [see reference 37] such that ‘cuts to the funding of the Health Protection Agency should be reversed and additional necessary funding be provided’ and ‘deplores the government’s decision to continue cuts and maintain financial restraints under the arms length body review at a time of increasing threat from pandemic influenza’. [see reference 38]