Pandemics: Can we learn the lessons of history?
In 1918 the world was already devastated by WW1, then further devastated by the influenza pandemic “Spanish flu”. It affected ~ 500 million people globally, leaving a death toll of 30-50 million. Unlike most influenza, which kill the weak, young and elderly, the H1N1 strain was claiming the lives of young healthy adults. The death toll was higher than the total casualties of the war. Towns banned visitors, some places even banned hand shaking. Churches and schools were overrun with the sick, undertakers were turning people away, telling people they had to take care of burying their loved ones themselves. This was a highly infectious disease, so one can understand the panic that people were experiencing. It was so prevalent that remote islands in the Pacific were affected. Fast forward almost 100 years to 2014. The world again is in a panic over the Ebola virus. Individuals outside the White House are holding placards reading, “Stop the Flights”. However this time, panic is spreading through misinformation and constant media sensationalism. Ebola is a low transmittable disease. Therefore have we learnt nothing in the last 100 years? We are more informed, medically superior, yet panic more in regards to a spread of a deadly virus in a remote part of the world. So are we ready for the next pandemic?
I attended a lecture entitled, “Pandemics: Can We Learn from History” at the Imperial War Museum London. The lecturer was Michael Baker, Professor of Public Health at the University of Otago, Wellington. Professor Baker is a world renowned scientist of infectious diseases, epidemiology and environmental health. He has worked internationally with the World Health Organisation (WHO) and the US Centres for Disease Control and Prevention (CDC). The aim of this talk according to Professor Baker, was to move beyond the epidemiology of pandemic diseases and consider what can be learnt. Scientific knowledge, enhanced visibility, social justice and global governance in helping us respond effectively to these major health challenges.
The evening started with a clip from New Zealand’s own, Peter Jackson’s 1992 B-movie Brain Dead. A film where an individual is bitten by a Sumatran rat monkey, gets sick and dies. The character then comes back to life to kill and eat dogs, neighbours and friends. If one gets bitten, the only way to beat the disease is to cut off the limbs of the infected. Much blood and gore follows. Of course this is a silly movie, but it does almost reflect some of our thoughts of what might happen if such a disease were to occur. Later movies such as 1995’s Outbreak and 2001’s Contagion do nothing to calm our nerves. These movies coincide with the interest at that time in emerging infectious diseases.
Professor Baker explained that Australia has some truly nasty emerging infectious diseases, which if you are an epidemiologist is very interesting. One of the diseases, the Hendra virus (HeV), is a particularly horrid zoonotic (infections that spread from animals to humans) disease affecting horses and humans. It has a 50% mortality rate in humans. It is still a relatively rare disease, but this an example of the kind of outbreak that Professor Baker tracks and reports. He looks at diseases that have the potential to become pandemics, diseases that cross borders to become a worldwide phenomenon as opposed to epidemics that are localised to countries or specific areas. The idea of a localised epidemic becoming pandemic. Mathematicians are able to predict the behaviour on a scale of how infectious a disease is, such as highly infectious Measles, to low infectious Ebola.
Problems arise when agents are submitted without being symptomatic. They will not be vulnerable to being controlled. This is why HIV is not easily controlled as individuals are able to live many years with no symptoms. Whereas diseases such as SARS are easily controlled and contained because symptoms occur rapidly. The critical element in worrying about the likelihood of a pandemic is the fatality risk. It is worth noting however that the term pandemic is still quite imprecise, many people have different dimensions as to what equates to a pandemic in regards to severity of a pandemic or whether it is asymptomatic. An epidemic may be more devastating in severity to a particular region than a pandemic. Asia is experiencing devastating epidemics in regards to the H5N1 virus. H5 viruses are avian influenza that effect the digestive symptoms of birds compared to H1 viruses in humans affecting the respiratory system. Now H5 viruses have mutated in such a way that they can affect humans with devastating effects, causing high mortality rates.
International health regulations have now been established, which is a global agreement of all 193 members of the WHO in understanding new diseases, and what we should be concerned about. They will look at what is an ‘extraordinary event’, and decide if it is a risk to other states and need a coordinated response. All countries signed up for this and use a decision tree, which is a risk assessment of a particular outbreak, such as an outbreak of H5N1, the pandemic that everyone has been awaiting for over a decade.
Another category that has the potential of pandemic are the synthetic, or weaponised infectious diseases. As the science in molecular techniques and understanding of genetics has become so sophisticated, so has the potential to synthesize new genetic material, able to mimic the most devastating effects of some of the worst infectious pathogens. The fact that it is now possible to exhume old influenza viruses and experiment with them is a very scary thought. Every year the United States releases security threats of this nature, the intentional release of pathogens or the use of weaponised agents.
Then there are the exotic infectious diseases from developed countries that can clearly have pandemic potential carried by vectors such as flies and mosquitoes, such as the Zika virus that has had a resurgence in the Pacific. Additionally there is the reintroduction of diseases such as polio and measles. It is now showing that a human factor, especially with measles as to how easy an outbreak can occur. The fact that there are vaccines available and children are not being vaccinated due to misinformation about possible side effects.
Imported food and drinks with contaminants is one area that they are not just thinking about infectious agents but the full spectrum of hazards such as chemical, microbiological and radiologic. The way these affect people behave in the same way as infectious agents in how they are transmitted. An example of this was the botulism found in New Zealand baby formula which had effects similar to a pandemic.
So by looking into the history of pandemics, are we able to predict the future? One of the goals is to look at what might work. For instance would closing schools make a difference through past observational studies? One can look to the First World War were extensive records exist. In New Zealand 5% of mortality rates were due to the Spanish flu, which added to the burden of warfare. The highest mortality rate were soldiers stationed in military camps and troop ships, usually in cramped conditions were it was difficult to quarantine and isolate the infected. Research has been done into the factors to help determine the likelihood of survival or mortality if such an influenza pandemic were to occur using a case controlled study. The 1918 pandemic showed that determining factors of mortality was age, chest diameter and other well defined features. The positive relationship link between mortality and chest diameter, indicating that larger men were more vulnerable, raising the likelihood of a cytokine storm causing very swift death upon catching influenza. Further research is being done to confirm this possible factor.
Professor Baker put forward that there are 5 major lessons we can learn from the last 100 years of pandemic diseases.
High Impact, they generally increase in inequality in effect and driven by inequality, high level of unpredictability, often highly controllable and will generally cause panic and outrage. Literature from the past really shows how pandemics shaped the world at that time but how can we use these for modern times? Through sophisticated modelling, if the Spanish flu were to occur, we would likely see >60 million fatalities. These kind of events will also have an extensive economic impact. When SARS occurred, even though only ~10,000 cases were documented, it had a multi-billion dollar impact, especially in Asia. As for inequality, pandemics are far more likely to occur in poorer societies and poorer populations in a differential way, how much more likely are you to die in a poorer country as opposed to Europe. This kind of effect can be seen in the mortality rates from Aids in Africa compared to the United States and Europe. Obviously there are other factors involved, such as likelihood of testing, unknown transmission and to availability to medication. However it is a prime example of mortality rate due to inequality. Pandemics that start in poorer countries due to inequality, it is more difficult to predict the outcome of a disease from a smaller sample as they are not representative of the larger population in general. Optimistically it shows that controllability of a pandemic is good as long as the disease is not asymptomatic. When looking at SARS, it had a high transmission rate but was highly symptomatic and very little asymptomatic transmission making it highly controllable. Influenza pandemics however are a lot less controllable and airport screening has proved ineffective with low sensitivity and specificity. Panic and fear which normally leads to prejudice and xenophobia usually arises due to how an outbreak is managed and is usually elevated due to miscommunication and misinformation.
Professor Baker and the NZ-UK Link foundation Visiting Professorship lecture programme 2015 can be seen at the following events.
4th June 2015 12-3pm The Wellcome Trust.
2nd July 2015 6-8.30pm London School of Hygiene & Tropical Medicine.
15th July 2015 6-8.30pm City of London, Guildhall.
By Darren Carty, second year student, BSc Honours Biological Sciences (Molecular Biology & Genetics)