The interest in viral diseases has been on the rise for both insurers and investors. In this article from RGA's ReFlections newsletter, Dr. Dan Zimmerman examines three noteworthy viral infectious pathogens, describes their clinical and epidemiological characteristics, and assesses their risk to both the general and insured populations.
Viruses are the most abundant and diverse biological entities on Earth, with a staggering 10 nonillion (or 1031) viral particles existing in all habitats at any point in time. They can infect all types of organisms, ranging from animals (including humans) and plants to bacteria and archaea. The Global Virome Project estimated the existence in birds and mammals of 631,000 to 827,000 viruses with the potential ability to infect humans. A recent study created an atlas of human viruses derived from public databases and produced the online Human Virus Database (HVD), containing 1,131 virus species documented to infect humans.1
Humans survive in the virus-filled world relatively free of disease primarily because viruses are very selective about which cells they infect. Only a tiny fraction of viruses poses any threat to humans. However, as SARS-CoV-2 taught the world, outbreaks of novel human illness do occur, which is not unexpected. In fact, most new infectious diseases cross over to humans from animals, at which point they are referred to as zoonoses. For a virus to successfully jump to a new species, it must overcome a number of biological hurdles. Then, it needs to be able to spread within members of that new species. These “spillover” events are often dead-ended and never progress beyond the first individual; however, some do succeed.2
A(H5N1) or H5N1 bird flu viruses first emerged in southern China in 1996. Those viruses caused large poultry outbreaks in Hong Kong in 1997, which resulted in 18 human infections. The 1997 bird outbreak was controlled, but the H5N1 bird flu viruses were not eradicated in birds and resurfaced in 2003 to spread widely throughout Asia, and later in Africa, Europe, and the Middle East, causing poultry outbreaks and sporadic human infections.3,4
The H5N1 virus is described as “highly pathogenic avian influenza” or HPAI and refers to mortality in experimentally infected poultry that, importantly, does not necessarily correlate with the severity of human infections. Nonetheless, H5N1 virus infections have been reported in more than 925 people, with approximately 50% case fatality rates (CFRs) since 1997, including 20 cases and seven deaths in Hong Kong between 1997-2003.5 Bird flu viruses currently circulating in wild birds and poultry in much of the world are genetically different from earlier versions of the virus, and multiple spillover events to mammals have been documented in several countries.3
The most recent concerning development stems from an outbreak of H5N1 in dairy cows in the US, first reported on March 25, 2024. As of November 2024, 508 dairy herds in 15 states have been affected. Several farm workers have been infected, but they generally present with mild symptoms that include conjunctivitis. Notably, human-to-human transmission has not been documented. H5N1 can be detected in raw milk; however, pasteurization does cause inactivation of the virus.6,7 Vaccines for H5N1 do exist and evidence suggests these would be protective, if needed, until updated versions of the vaccines could be developed and produced.8
There is concern H5N1 could present a pandemic risk in humans. However, it has not acquired the capability of human-to-human transmission since its emergence. Both the US Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) currently deem the pandemic risk as low, while the risk of infection for occupationally exposed persons is low-to-moderate, depending on the risk mitigation measures in place.9,10 Nonetheless, careful monitoring is required to detect any changes in transmission patterns or case frequency in humans that could signal a significant impact on public health.
Dengue is an Aedes mosquito-transmitted virus and a significant global health threat. Dengue fever is the leading cause of arthropod-borne viral disease worldwide. With over 100 million cases annually resulting in approximately 25,000 deaths, dengue has produced epidemics across different regions globally.
Dengue is caused by four distinct, but closely related, viruses abbreviated as DENV-1, -2, -3, and -4. While infections are asymptomatic in up to 75% of affected individuals, the disease ranges from self-limiting dengue fever to severe hemorrhagic shock. A fraction of infections, between 0.5% and 5%, develop into severe dengue; however, a second infection with a different type of DENV increases the risk of severe dengue. Without proper treatment, fatality rates can exceed 20%, particularly among children.11,12,13
The incidence of dengue fever has increased dramatically over the past few decades, and the infection is now endemic in some parts of the world, possibly due to increased global travel. Climate change may also be playing a role in the expansion of dengue-carrying Aedes mosquitoes into more temperate regions of the world and to higher elevations. Nineteen percent of the current global dengue burden is attributed to climate change and could increase by 40%-60% by 2050. In the US, local transmission of DENV has been limited, with sporadic cases or small outbreaks in Florida, Hawaii, Texas, and the US Virgin Islands. However, confirmed local DENV transmission has been reported in Arizona and California in recent years. Additionally, a major DENV outbreak was declared in March 2024 in Puerto Rico.11,12,13,14,15
Infection with one type of DENV induces life-long protection against infection from that specific DENV but not against the others. Two dengue vaccines have been developed and are used in countries with high dengue transmission intensity. Vaccination does not prevent all cases of dengue, and other strategies should be employed, including vector (mosquito) control.16
For insurers, collaboration among actuaries, medical directors, and data scientists is necessary to monitor and assess infectious disease risk as it evolves over time.
Marburg virus (MARV) first emerged in 1967, when lab researchers in Marburg and Frankfurt, Germany and Belgrade, Yugoslavia were infected with a previously unknown infectious agent. The 31 patients (25 primary, six secondary infections) developed severe disease that led to the deaths of seven people. The original source of infection was African green monkeys that had been imported from Uganda. An etiologic virus was identified within three months and was named after the city with the most cases. MARV is clinically similar to Ebola virus, and both are now classified as Filoviridae, due to their distinctive thread-like structure. Since the original outbreak in 1967, 17 subsequent MARV outbreaks have occurred, primarily in African countries.17
Marburg virus disease (MVD) occurs after prolonged exposure to mines or caves inhabited by certain types of fruit bats, which are the virus' reservoir. The virus can spread from human to human via direct contact with blood, secretions, organs, or other bodily fluids. Healthcare workers are frequently infected by patients. Symptoms include high fever, headache, and fatigue. Gastrointestinal symptoms, including diarrhea and abdominal pain, subsequently develop. Hemorrhage can occur with bleeding from multiple areas of the body. There is no treatment for MVD other than supportive care. Case fatality rates (CFRs) have varied, depending on the location of the outbreak, but are quite high - between 24% and 88%.18
The most recent Marburg virus outbreak began in Rwanda and was reported by the Ministry of Health on September 27, 2024. As of November 11, 2024, 66 cases and 15 deaths (CFR = 23%) have occurred. No cases have been detected outside of Rwanda, and the risk to distant countries, including the US, is low. However, a risk of spread to other countries by infected travelers from Rwanda remains. As a comparison, during the Ebola outbreak of 2014, no community spread occurred in the US after two case introductions and seven medical evacuations. Trials with an investigational vaccine are underway, with an emphasis on preventing MVD in healthcare workers.19,20
Viral infectious diseases continually provide challenges to public health officials and insurers. While some are deemed low risk, vigilance must be maintained as drivers, such as climate change and international air travel, can widen the geographic range of viral diseases. Additionally, viruses that currently do not have human-to-human transmission capability can acquire it, leading to significant public health impacts. For insurers, collaboration among actuaries, medical directors, and data scientists is necessary to monitor and assess the risk as it evolves over time.
RGA experts are eager to engage with clients to better understand and tackle the industry’s most pressing challenges together. Contact us to learn more about RGA's capabilities, resources, and solutions.
