Theme: This analysis looks at risk scenarios that Spain could face in the not very unlikely event that the country becomes affected by a human influenza pandemic in the future.
Summary: At present a human influenza pandemic is little more than a theoretical possibility. However, and due to the spread of the avian influenza and the fact that there have been cases of bird-to-human transmission, the WHO has issued a pandemic alert to the effect that a new influenza virus subtype is causing disease in human beings but is not yet spreading efficiently and sustainably among the human population. This suggests that the time is ripe for adopting some preparatory action with a view to minimising the damage that could be caused by a pandemic. This analysis assesses the current situation with regard to a possible pandemic caused by the H5N1 virus responsible for avian influenza. The conclusions suggest that apart from careful planning regarding health issues, it is also necessary –at the very least– to plan how to deal with security-related issues in the event of the pandemic entailing a more severe outcome than in the world’s last two pandemic experiences.
Analysis: Over the past year there has been a gradual increase in media attention on the avian influenza epidemic. Interest is now escalating further as the disease, after having been contained in Asia for several years, is becoming a pandemic that has so far affected three continents –Asia, Africa and Europe–. Given the mounting information about the disease’s diffusion, there is a risk of overexaggerating the current risks and underestimating the future risks.
As its popular name indicates, avian influenza mainly affects poultry and wild birds. As is the case of human influenza, it can appear in multiple forms, although there are two main variants: (1) the so-called ‘low pathogenic’; and (2) the ‘high pathogenic’. While the former causes mild symptoms and might even go undetected, the latter is far more virulent. In its highly pathogenic version the virus spreads extremely rapidly in poultry flocks and has a mortality rate approaching 100%, often within 48 hours. One of the virus subtypes causing avian influenza in its highly pathogenic form is known as H5N1, and is probably one of the most dreadful bird-to-bird influenza viruses of all time. It is this subtype that is now spreading very rapidly across Asia, Europe and Africa, transmitted by migrating wild birds. However, a common feature to all avian influenza viruses is that they are species-specific. That is, the virus is primarily transmitted from bird to bird, and with few exceptions the only real victims of the avian influenzas are the world’s bird populations.
So if the virus is considered to be species-specific to birds, why should humans fear it? There are two main reasons. First, on very rare occasions infected birds have passed on the virus to human beings with very severe consequences. According to the WHO, from 2003 to February 2006 there have been 173 known cases of people who have contracted the illness after having been in close contact with birds infected with the H5N1 virus, of which 93 have died.
Although the seriousness of the possibility of the virus’s bird-to-human diffusion should not be underestimated, neither should it be exaggerated. As indicated by the data above, the risk of infection in this direction is extremely limited considering the number of people that live in South-East Asia –the region that so far seen the largest incidence of bird-to-human infection and probably has the largest population of poultry– and that are exposed to contact with birds. However, the fact that birds can pass on the virus means that the necessary precautions should be taken to avoid such a possibility. The actions undertaken by governments throughout Europe –heightened monitoring of wild bird deaths and the isolation of poultry from outside contact as a result of reports of the presence in Europe of wild birds infected with the H5N1 virus– are good examples of what can be done to prevent the virus from spreading further among the bird population. Simply put, the logic behind this is that the more infected birds there are the higher the risk of bird-to-human transmission.
The second reason why human beings should beware an avian influenza pandemic among the world’s bird population is still only theoretical, but of far greater concern. There is a theoretical risk that the virus might undergo genetic changes that enable it to break through the species barrier. In a worst-case scenario this could lead to the emergence of a mutated virus with the capacity to infect human beings by air and to be easily transmitted from person to person. Other scenarios, considered less likely by most experts and by the media, include the emergence of a mutated virus that would affect other species, such as livestock and pigs, with serious consequences for human food chains, in a similar way that the virus is currently causing havoc in the supply and consumption of poultry (one of the main sources of animal food for human beings). Regardless of the scenario, any genetic expansion of the virus that provides it with an infectious capacity beyond its current species barrier could come at a very high price. Should human-to-human transmission become a possibility, there could be a global influenza outbreak (a pandemic) with more or less serious implications for human health, security and the world economy.
The genetic transformation necessary to enable the virus to be transmitted from human to human is possible through: (1) the combination of the H5N1 strain with an existing human influenza virus, thereby allowing it to bridge the species barrier; or (2), a gradual self-generated genetic evolution whereby the virus expands its host range.
Both transformation scenarios gain credibility as the incidence of infection in birds increases. In addition, the likelihood of a genetic combination increases in line with the possibility of contact between infected birds and other species (particularly human beings), which follows more or less naturally from the first condition. This is why it is so important to contain the disease in birds and prevent it from spreading geographically and why firm action is being taken by the government of countries that have detected the presence of the H5N1 virus in their territory. The problem, however, is that while recent events clearly indicate that human intervention has probably been successful in delaying the geographical diffusion of the H5N1 virus among birds, it has failed to prevent its spread to Europe and Africa. This means that despite the efforts undertaken, the virus now has far greater opportunities to mutate.
Recent developments in Africa are particularly worrying. The H5N1 virus is spreading in a more or less uncontrolled manner among Nigeria’s bird and poultry populations. Neighbouring Niger has reported cases and there are strong indications that large numbers of poultry have died in Ethiopia as a result of H5N1 infections. If the virus manages to establish itself securely on the African continent, its chances for mutation would increase very significantly.
Nevertheless, it is impossible to say with any certainty that the virus known as H5N1 will have the capacity to transform itself into a human influenza virus. Regardless of any preventive measures aimed at containing it and preventing further bird-to-human transmission of the disease, the virus might be so far from acquiring human-to-human transmission capacity that it will never appear in a pandemic form. Hence, at this stage it is simply impossible to know whether the H5N1 virus poses any real and significant threat to human health. However, empirical evidence suggests that it could indeed be very likely for the virus to become a problem of great concern to human beings.
It is not the first time that an avian influenza virus becomes capable of human-to-human transmission. The last two world pandemics –in 1957 and 1968– were caused by an exchange of genetic codes between avian influenza and human influenza viruses. The same occurred with the 1918 ‘Spanish flu’ pandemic. However, in contrast with the 1957 and 1968 outbreaks, experts now believe that the 1918 pandemic was caused by the virus H1N1 that initially only affected birds, but which through a series of gradual self-generated mutations acquired the capacity for human-to-human transmission without any genetic code exchange with a human virus. Although there is a possibility that H5N1 could combine with a human influenza virus, the WHO maintains that it might follow the same evolutionary path as the H1N1 virus –that caused the pandemic in 1918– is thought to have followed. There are also other similarities between the H5N1 and H1N1 viruses. In the rare cases where birds have passed on the H5N1 virus to humans it is usually the young and healthy population that run the highest risk of becoming infected and dying. When the H1N1 virus attacked human beings in 1918 it preferred the young and healthy rather than infants and the elderly, who are the main target and risk groups in cases of normal influenza and even in pandemics –as in 1957 and 1968–. Finally, and in contrast to the 1957 and 1968 pandemics, the H5N1 and the H1N1 viruses both have the capacity to provoke primary viral pneumonia in the absence of secondary bacterial infection, which significantly increases their lethal capacity.
To summarise the situation, there are two possible outcomes as regards the H5N1 virus: (1) The virus never mutates and, hence, there is no immediate threat of a pandemic; and (2) At some point in the future the virus acquires human-to-human transmission capacity –through either (a) an exchange with a human influenza virus or (b) through gradual adaptation (see Illustration 1)–. However, even if H5N1 does not cause a human influenza pandemic, another ‘new’ emerging avian influenza virus could possibly do so in the course of this century, hence the loop in the “No Mutation” case in Illustration 1. If the virus were to suffer a transformation, this would almost certainly mark the start of a pandemic, largely because the H5 virus subtype has never circulated among human beings. The vulnerability or susceptibility of the world’s population to a mutated H5N1 would therefore be universal.
As for the most likely outcome of a virus transformation, the level of severity of the resulting pandemic can be expected to be determined by the type of transformation. If the virus ends up exchanging genetic codes with a human influenza virus, the human population is likely to have some resistance to the ‘new’ resulting virus since many people might have been exposed to at least one of the new virus H and N subtypes. This is the reason given by some experts as to why the pandemics in 1957 and in 1968 were far less severe in terms of mortality than the pandemic in 1918, when the virus mutated gradually by itself without the interference of a human influenza virus. As mentioned above, experts have observed that the way the H5N1 virus is currently evolving does not rule out the risk of a severe pandemic similar to 1918 and 1919. Nevertheless, since there is no way of foreseeing what form a pandemic virus might take, the most rational approach to the threat of a global pandemic would be to prepare and be prepared for a broad variety of situations. Hence, in order to deal effectively with the threat, the important question is: what is the potential damage to be expected from an influenza pandemic?
Given the uncertainty regarding the virus’s capacity to inflict damage once it has acquired a human-to-human transmission capacity, it is extremely difficult to forecast the damage it can cause on society. However, what can be done is to draw on the knowledge about the damage caused by previous pandemics.
The problem with this approach is that data is exceptionally scarce, particularly regarding attack rates, hospitalization statistics and data on the need for medical assistance. There are several reasons for this. One of the main reasons, however, is that the large number of influenza cases are never reported since people stay at home while suffering only mild symptoms. Another important reason is that influenza is not diagnosed directly, but rather according to the symptoms it causes. The only reliable data that exist are mortality rates. Hence, the simplest way to assess the potential impact of a pandemic is to assess the excess mortality observed in each year in which there is a pandemic.
Figure 1 shows the reported mortality in Spain between 1910 and 1970. Pandemic years are marked in red. It can be appreciated that the 1918 pandemic was completely out of the ordinary. The total mortality for that year approached the 700,000 mark, the largest number of fatalities than in any other year on record in Spain’s history. How many of these fatalities can be attributed to the ‘Spanish Flu’?
One way of assessing the excess mortality is to compare the total mortality with the average total mortality in the 5 years preceding the pandemic. This shows that the excess mortality in 1918 was of approximately 240,000 people, or approximately 1.163 dead per 100,000 inhabitants (Spain had a population of around 21 million at the time). That is, had there not been a pandemic in 1918 around 240,000 people less would have died.
While 1918 was by any measure an exceptional pandemic year, the pandemic years 1957 and 1968/69 (Spain was affected by the 1968 pandemic in 1969) are harder to tell apart from a ‘normal’ year. The reason for this is that the two later pandemics were caused by a less lethal virus than the H1N1 virus responsible for the 1918 pandemic. Nevertheless, by the same procedure as above it can be calculated that in 1957 and 1969 the excess mortality was respectively around 26,000 and 34,000. Controlling for population size this translates into respectively around 59 and 78 people dead per 100,000 inhabitants.
The WHO, in assessing the potential lethal impact of a new pandemic, usually refers to considers the 1957 and 1968/69 pandemic death rates the most likely. However, since the H5N1 virus has demonstrated its capacity to kill people when they are infected by birds, and since there is probably not going to be an effective vaccine until six months after the onset of the pandemic (and then only in limited quantities), there is no assurance that existing anti-viral drugs will be effective against the new virus. As a result, there is a possibility that a pandemic caused by a mutated H5N1 could be as deadly or even deadlier than the virus that caused the 1918 pandemic. Such a nightmare scenario could entail a potential total death toll of between 250,000 and 500,000 in Spain alone.
However, it is not only mortality that is an issue in assessing the possible impact of a new pandemic. Other issues, such as the number of people falling ill and the number of people that require some form of medical assistance, are also important to consider. Studies aimed at assessing the general impact of an influenza pandemic typically cite 30% as a likely overall attack rate in a population in a developed country never before exposed to a new virus subtype. Of course, the number could be much higher. Attack rates of between 30% and 70% have been observed in developed countries in all three pandemics. But for the sake of simplicity it can be assumed that a 30% attack rate is reasonable, suggesting that around 13 million people in Spain could possibly fall ill in the event of a pandemic becoming a reality. It is important to note that the attack rate is likely to be high regardless of the virus’s severity in terms of mortality. To understand the magnitude of such an attack rate, in a normal year around 10% to 15% of Spain’s population is affected by influenza and the number of diagnosed cases ranges around the 2 million mark, or 4% to 5% of the total population.
Furthermore, studies aimed at assessing the impact of pandemics on the health care system estimate that around 45% of those affected require some form of medical attention/consultation, and that a fraction of these require hospitalization. This suggests that the Spanish health care system might have to be prepared to attend close to 6 million people in the course of two to three months.
Data on hospitalization rates in pandemic years are difficult to come by, and are usually only available for the 1957 and 1968-69 pandemics. One of the few studies reporting the excess hospitalization rate for the 1968-69 pandemic indicates a spike of 140% compared with a year of low epidemic activity. For 2003, Spain’s Instituto Nacional de Estadística reported a 236/100,000 rate of pneumonia and influenza hospitalization. The Centro Nacional de Epidemiología classified the 2002-03 influenza season as a low activity season. This means that in the event of a pandemic similar to those of 1957 and 1968-69 around 100,000 more cases of hospitalization could be expected than in a year with low influenza activity. However, hospitalization rates are dependent on the virus’s virulence and some experts do not rule out a 10-fold increase in the hospitalization rate should a pandemic be caused by a virus with a similar lethal capacity to the 1918 strain.
Illustration 2 summarizes the potential impact that could be caused by the data reported above, for three different scenarios: a Mild Scenario, a Middle Scenario and, finally, a Severe Scenario. It should be borne in mind that all three scenarios are only indicative. Slight changes in the attack rate, or in any other assumption regarding the other variables, would immediately render them useless. The purpose is simply to illustrate the potential damage that a new pandemic could have on Spanish society, given a set of fixed assumptions.
The first scenario is based on the 1957 and 1968-69 pandemics. The assumptions regarding excess hospitalization are a 50% to 100% increase compared with a ‘normal’ year. Excess mortality is assumed to be 68/100,000 inhabitants, which is in between the excess rates reported in the two pandemics. The Medium Scenario assumes a more virulent virus. It foresees a 2.5 increase in excess hospitalization and a mortality rate of between 260 and 560/100,000 inhabitants. The lower limit corresponds to half the mortality rate registered in the US in the 1918 pandemic and the upper limit is approximately equal to the US mortality rate for that year. Finally, the Severe Scenario extrapolates the mortality rates observed in the 1918 pandemic, where the lower level corresponds to the rate observed in the US, and the upper limit to the rate observed in Spain. The hospitalization rate is assumed to be approximately ten times greater than in a normal influenza year. Note that all three scenarios assume similar attack rates and a similar number of people requiring some form of medical assistance.
What are the consequences for society of the three scenarios? There is little doubt that all three scenarios would require an extraordinary effort from the country’s healthcare system in terms of medical assistance. It should also be considered that those employed in health-related services are equally susceptible, if not more, to a pandemic virus than the population at large. If close to 30% of the country’s healthcare workers become ill, the system would have to cope with double the workload while running at only two-thirds of its capacity. Hence, it can be concluded that any pandemic, regardless of its severity in terms of mortality, would put the healthcare system under significant pressure. Advanced planning would be absolutely necessary to avoid the system’s breakdown as well as to ensure the necessary means for delaying any further diffusion of the virus.
To this end the Spanish Ministry of Health and Consumption has developed a National action plan for an influenza pandemic (Plan Nacional de Preparación y Respuesta ante una Pandemia de Gripe, see: http://www.msc.es/ciudadanos/enfLesiones/enfTransmisibles/pandemia/home.htm).
The plan follows the recommendations issued by the WHO and its successful implementation will be required to avoid the possible breakdown of the country’s healthcare system in the midst of a pandemic regardless of the scenario. Of course, no matter how well thought out the national plan is, if those involved in making the plan operational are unaware of what is expected of them, there is the possibility that the plan fails to achieve its objectives. Thus, at this stage, the Spanish authorities should probably be concerned with the problem of how to successfully inform all the stakeholders encompassed by the plan about what is expected of them with sufficient time to act should a pandemic materialize. Since the plan virtually counts on the cooperation of all private and public institutions and organizations as well as on the population at large, the task is definitely not as easy as could be imagined. Informing the general public could easily cause an alarm. Few people are aware of the potential risk of a pandemic and most people still believe that avian flu is about not consuming poultry, and in the remote case that it should become a human influenza, faith in the medical system is such that the potential risks are shrugged off. Regardless of the virus’s virulent capacity, if ordinary citizens and employers fail to cooperate with the objectives laid out in the plan the economic damage to society might rise disproportionately since both attack rates and hospitalization rates would rise significantly.
However, if mortality rates rise very significantly as described in the medium and severe scenarios, more problems than just health issues might start to emerge. A significant rise in mortality rates would automatically be followed by an equally significant rise in the propensity to panic. Should panic become widespread the pandemic would imply both a state-wide and a world-wide security risk.
The first problem to arise would be how to protect the healthcare system and its employees in a situation of public panic. Also, a large part of the medical assistance necessary in a pandemic situation is sustained by ambulatory healthcare workers, making house calls. This would be particularly true in a severe scenario since the logistic capacity of hospitals would be far below the actual demand during a severe pandemic (Spain has around 150,000 hospital beds and in the worst-case scenario the demand could rise to up to 1 million). Ambulatory work could become associated with certain risks if the pandemic is accompanied by mortality rates significantly higher than predicted by a mild scenario based on the experiences of 1957 and 1968-69, and it is possible that medical personnel could come to require some form of protection and assistance to be able to carry out their tasks effectively. Furthermore, if hospital capacity is exhausted the healthcare system would have to rely on the police and armed forces to set up ambulatory hospitals and provide the necessary logistics to keep them functioning.
Other problems that would emerge would be the need to maintain basic services in a society in a state of decomposition. Water and food supply chains would have to be secured, as well as distribution channels and transport facilities. A natural catastrophe of this magnitude would also imply a rising crime rate and would require effective measures to protect property.
A further complication is that Spain is highly dependent on gas and oil for its energy supply, with close to 100% being imported from abroad. A pandemic is a global event that implies the same risks world-wide. Thus, if the mortality rate approaches the levels recorded in the 1918 pandemic, there could be a serious global disruption of the social order and of the distribution of goods and services. This could lead to serious difficulties in the supply of energy. A cut in energy supplies would seriously hamper any effort to deal with all the different situations –whether health or security related– brought about by a pandemic.
Furthermore, similarly to healthcare workers, the police, Civil Guard and army –the key actors on the security front– would also be exposed to the pandemic’s health risks. The general mobilisation of the country’s security forces might result in an operational level of only two-thirds, or probably less, of their full capacity.
Conclusion: In preparing for the possibility of a pandemic, and since it cannot be ruled out that it might be caused by a strain of the H5N1 influenza virus that has proved to have a lethal capacity at least at par with the virus that caused the 1918 pandemic, it is essential to broaden the necessary preparatory work to include state institutions other than the health authorities. If mortality rates approach the levels recorded during the 1918 pandemic, issues of state security might rapidly gain importance. Thus, the existing National Action Plan for an influenza pandemic should be accompanied by a National Plan to deal with security-related problems resulting from extreme mortality rates. Such a plan should at the minimum cover the following:
(1) Ensuring the country’s healthcare facilities and staff are fully operational in a potential situation of public panic throughout all the phases of a pandemic, as well as assisting in widespread distribution of medication and vaccines when and if available.
(2) Setting up ambulatory hospitals and providing the necessary logistics to make them operational.
(3) Ensure the provision of basic services and the supply and distribution of water and foodstuffs.
(4) Ensuring public order and preventing looting and criminality.
(5) Preparing back-up services in the event of a disruption in the country’s energy supply as well as considering and planning for other severe disruptions in international trade of vital importance.
In addition to the necessity of preparing plans to ensure state security in the event of a severe pandemic scenario, it is also important to promote the awareness of how state security can be affected by a natural catastrophe. This has become even more important in light of the large-scale environmental changes predicted by the scientific community. Furthermore, a forthcoming pandemic might not be the last one to appear in this century. Hence, the in-depth study of possible solutions to the security problems posed by Mother Nature, whether biological –as in the case of a pandemic–, seismic, man-made or weather-related is probably a sound investment for our future.
Senior Analyst, Demography & Population, Elcano Royal Institute