Tag Archives: pandemic

A Coup Against Flu?

Recent articles from two separate research groups published in Science and Nature Medicine report major breakthroughs in flu vaccine research. The advances could ultimately lead to the holy grail of influenza prevention–a universal flu vaccine.

By conferring immunity against large numbers of flu strains, the new vaccines have the potential to reduce the severity of seasonal flu outbreaks and vastly reduce the risk of novel pandemics.  Using the RMS Infectious Disease Model, we calculated that if such vaccines were able to confer immunity to 50% of people globally, the risk of a novel flu pandemic outbreak could be reduced by as much as 75%.

This would be a huge success in reducing the risk of excess mortality events and improving global health. Though I should emphasise that while Edward Jenner invented the smallpox vaccine in 1796, it took until 1980 for smallpox to be eradicated from the wild. Beyond development of effective broad-spectrum vaccines, there is a lot of work to do to make the world safe from flu.

A high proportion of flu victims are the elderly. Significantly reducing deaths from flu would disproportionately reduce old-age mortality. This is particularly interesting; not only is it an important milestone in improving old-age public health, it is also relevant to old-age care and budgeting for retirement too.

Influenza Is The Most Likely Source of Future Pandemic Sickness and Mortality. 

In the U.S., in a single flu season, the average number of flu-related deaths is 30-40,000, peaking at 47,000 deaths in previous seasons. This does not take account of the viruses that can cause major pandemics: death tolls in the 1918 “Spanish Flu” event reached as high 50-100 million people worldwide. 

Widespread use of a universal vaccine conferring lifelong immunity could eliminate these deaths, making a meaningful contribution to reducing infectious disease mortality.

Structure of influenza, showing hemagglutinin as HA. Source

The marvel of the new vaccines under development is their potential to confer immunity against many strains, including ones that have not yet emerged. They work by using cutting-edge molecular machinery to target the stem of the haemagglutinin protein on the virus’ surface. The vaccines have only been tested on animal models and only on a small scale so far, but have worked well in reducing viral loads and mortality in these tests.

If this breakthrough translates into future vaccines that prove efficacious in clinical trials, these could become immensely powerful in combatting both seasonal flu cases and reducing the likelihood of new flu pandemics.

Today, beyond seasonal flu, there are no vaccines capable of preventing novel flu pandemics. However, the production pipeline for the current seasonal flu vaccine can be put to use in pandemics, with current capacity of pipelines estimated to produce decisive quantities of vaccine within three months of a pandemic outbreak.

As quantified in the RMS Infectious Disease Model, while this current technology has the potential to substantially reduce the total caseload of a pandemic, it is not a panacea. Three months is a relatively long time for highly transmissible viruses, so very large numbers of people could be infected in this interval. Even more infections would happen during the roll-out period before the vaccine has successfully been given to sufficient people to halt the spread. Furthermore, complications could emerge during the production that either mean it takes longer than three months, or that such a vaccine only confers partial immunity.

RMS created the world’s first probabilistic model of pandemic influenza and the first probabilistic model of vaccine development, delivery, and efficacy. The recent breakthroughs in flu vaccine research are welcome news and RMS scientists are closely monitoring the developments.

Are fears of a global Ebola pandemic warranted?

Ebola is a hot topic in the media right now, with multiple cases being reported outside of West Africa and much confusion among the general public around the reality of the danger. So, are the fear and sensationalism warranted?

RMS models infectious diseases and recently developed the world’s first probabilistic model for the current West African Ebola outbreak. While Ebola is indeed a very scary and relatively deadly disease, with a case fatality rate between 69 and 73 percent according to the WHO, RMS modeling shows that it is unlikely the outbreak will become a significant threat globally.

The spread of Ebola in West Africa is in part due to misconceptions and fear surrounding the disease and a lack of public health practices. Ebola can be passed solely via bodily fluids; the risk of unknowingly contracting the disease is low.

Fear is prevalent among some West African communities that Ebola is a lie or is being used purposefully to wipe out certain ethnic groups, causing them to hide sick family members from healthcare and aid workers. Customary burial practices, in which family members kiss and interact with the dead, also have contributed to Ebola’s spread. Getting the populace in these countries to trust foreigners who are telling them to abandon their customs has been an uphill struggle.

In more developed countries where health care is more advanced and understood, the chances of transmission are exponentially smaller due to the fact that extreme containment measures are taken. Controlling the spread of the disease comes down to a question of logistics; if the medical community can control the existing cases and trace the contact made with carriers, spread is much less likely. For example, the case in Texas can be contained to one degree as long as every single person in contact with the patient is tracked.

There is also a (speculative) fear of the virus mutating into an airborne pathogen; the fact is, the chances of the virus changing the way it is transmitted, from fluid contact to airborne passage, are very low and of a similar order of magnitude to the chance of emergence of a different highly virulent novel pathogen.

Vincent Racaniello, a prominent virologist at Columbia University wrote:

“When it comes to viruses, it is always difficult to predict what they can or cannot do. It is instructive, however, to see what viruses have done in the past, and use that information to guide our thinking. Therefore, we can ask: has any human virus ever changed its mode of transmission? The answer is no. We have been studying viruses for over 100 years, and we’ve never seen a human virus change the way it is transmitted.”

The tipping point in the modeling of a virus like Ebola is the point where the resources being used to mitigate the threat outpace the increase in new cases. Trying to get ahead of the epidemic itself is like a race against a moving target, but as long as people get into treatment centers, progress will be made in getting ahead of the illness.

So, while Ebola is a very scary and dangerous illness, it is not something that we expect to become a global pandemic. However, while the current outbreak is not expected to spread significantly beyond West Africa, it still has the potential to be the most deadly infectious disease in a century and could have drastic economic impacts on the communities that suffer from Ebola breakouts. In fact, the economic impacts are likely to be worse than the actual impacts of the disease, due to negative impacts to trade and inter-community relations.

The key is to contain it where it is, reach the tipping point as quickly as possible, and to promote safety around existing infected persons. Through travel control measures and the development of several new drugs to combat the virus, the danger of epidemic should be drastically reduced in Africa and, as a result, the rest of the world.

Assessing the Risk of a Global Ebola Pandemic

With the current outbreak of Ebola in western Africa, as well as the recent MERS coronavirus and H7N9 avian flu outbreaks, the world is becoming increasingly concerned about the risk of emerging infectious diseases and their potential to cause the next pandemic.

As catastrophe modelers, how do we assess the risk of a pandemic?

To understand the potential dangers of Ebola, it’s helpful to look to the framework we use at RMS to model infectious disease pandemics. The RMS® LifeRisks Infectious Disease Model projects the excess mortality risk for existing infectious diseases, like influenza, as well as infectious diseases that are emerging or have recently appeared, like Ebola. When modeling a disease, we first look at two main criteria: the virulence and the transmissibility of the pathogen responsible for causing the disease. We then take into account mitigating criteria, including medical and non-medical interventions.


Virulence is a measure of how deadly a disease is, typically measured by the case-fatality rate (CFR), which is the proportion of people who die from the disease to those who do not. The current Ebola CFR is 55 percent. For comparison, the CFR for bubonic plague typically ranges from 25 to 60 percent. CFR for flu is typically less than 0.1 percent.



Transmissibility refers to how likely an infected person is to transmit the disease to another person, and is measured in terms of the basic reproductive number, or R of infection, which is the average number of additional infections one person generates over the course of illness. In order to cause an epidemic, R needs to be greater than 1.

The R for the current Ebola outbreak is greater than 1, and the disease will continue to spread. Past Ebola outbreaks have been estimated to be in the 1.3 to 1.6 range, but have occasionally been greater than 5, which is why there is cause for concern. However, Ebola is less transmissible than many other infectious diseases. For example, measles, which is highly transmissible, has an R of greater than 10 in an unvaccinated environment.


Societal and Environmental Factors

Societal and environmental factors can play a large role in transmissibility. In this case, societal and environmental factors in West Africa have contributed to the disease’s spread. For example, traditional burial practices in which families wash the deceased can expose additional people to the virus.

However, the risk of Ebola developing into a pandemic that extends beyond the region is low, due to the standard public health and infection control practices in place in many countries globally. Ebola can only be transmitted via direct contact with bodily fluids, especially blood, which means that caregivers are the primary people who might be exposed to the virus. In many countries including the U.S., the general practice is to treat all blood as potential sources of infection, due to experience with HIV and other blood-borne diseases. In quarantine situations, such as those being used with the American Ebola cases in Atlanta, the likelihood of transmission from a single person is miniscule.

Medical and Non-Medical Interventions

Medical and non-medical interventions mitigate the risk of an infectious disease pandemic. Typical medical interventions for infectious disease include pharmaceuticals and vaccines. Often, there is no specific therapy or drug available for new or emerging diseases. In these cases, we model the effect of supportive care, which includes management of blood pressure, oxygen, and fluid levels. As we’ve seen with the current outbreak, supportive care and the access to healthcare can vary substantially, depending on the region or population. With the exception of experimental treatments, there are no pharmaceutical interventions available for Ebola. Experimental Ebola drugs are not applicable to large populations at this time.

If there are high enough immunization rates, vaccines can reduce or stop the spread of diseases like measles or whooping cough. Unfortunately, a vaccine isn’t currently available for Ebola. Ebola outbreaks occur sporadically and are caused by different virus strains, making vaccine development more difficult.

In addition to vaccines and medical interventions, we account for non-medical interventions when modeling the impact of pandemics. Non-medical interventions include quarantines, school closures, and travel restrictions. Various countries in Africa have begun to implement these methods in hopes of stopping the spread of Ebola. However, these types of countermeasures can often be difficult to time or enforce properly. Ebola can have an incubation period from two days to as long as 21 days.

So, what is the pandemic potential of Ebola?

The current outbreak is now the largest outbreak of Ebola to date, and the World Health Organization (WHO) has designated the outbreak as a Public Health Emergency of International Concern. However, while cases will continue to develop, a global pandemic is unlikely. Even if the disease were to spread to other regions of the world, Ebola is still considered a rare disease and the transmissibility is likely to be much lower due to quarantine and infection-control measures, even if the CFR remains high. We have not seen any community transmission outside of Africa, and this is expected to continue. Ebola is a very serious disease, with devastating consequences to impacted communities. As risk managers, we aim to improve understanding of catastrophes such as pandemic disease so that as a society we can be better prepared to mitigate risk and recover from catastrophes.

Rebecca Vessenes contributed to this post. As a Senior Quantitative Modeler at RMS, Rebecca is involved in the development and parameterization of the LifeRisks longevity models. She recently completed the longevity model for Japan and has worked on determining the correlation structure for mortality improvement between countries. Prior to working for RMS, she led the Financial Modeling group at AIR. Rebecca earned a Ph.D. in mathematics from California Institute of Technology and is an actuary with the Society of Actuaries.