Arthropods, Pathogens, and Bioterrorism

By Chris Healey

Mosquitos are responsible for a chickungunya fever outbreak in the Caribbean several hundred miles off the United States coastline. That outbreak is an addition to the expanding role arthropods play in the spread of illness.

Many arthropods are erroneously classified as insects. While mosquitos, lice, and fleas are indeed insects with six legs, ticks have eight legs and are technically arachnids. The term arthropod is an overarching classification encompassing mosquitos, fleas, and ticks – all common disease vectors. Insects are arthropods, but not all arthropods are insects.

Arthropods spread several of the world’s most significant diseases. Notable among them are Lyme disease, typhus, yellow fever, Japanese encephalitis, West Nile virus, and, most significantly, malaria. Of the 45 select agents designated by the U.S. Department of Health and Human Services, 12 are transmitted by arthropods.

Diseases spread by arthropods have influenced some of the greatest conflicts in history. More French soldiers are suspected to have died from louse-borne typhus than actual combat during Napoleon’s ill-fated 1812 invasion of Russia. Staggering mortality among the French army forced Napoleon to renounce Moscow and retreat back to France. During WWII, mosquito-borne malaria was a serious health threat to U.S troops throughout campaigns in the South Pacific.

Several tick-borne bacterial illnesses have been endemic to North America since antiquity, including Lyme disease and Rocky Mountain spotted fever. In recent years, mosquito-borne viruses have made their way across U.S. borders. The introduction of West Nile virus in 1999 and a 2005 dengue hemorrhagic fever outbreak in Texas have solidified emerging and foreign arthropod-borne diseases as threats to U.S. public health.

Arthropods can also serve to carry out bioterrorism. Terrorists could utilize arthropods to execute clandestine bioterror attacks through exploitation of feeding behavior. Inoculation of arthropods with the desired agent and subsequent release into unsuspecting populations could spread illness during, or shortly after, blood meals. Although possible, that scenario is unlikely due to the difficulty associated with production and maintenance of pathogen-inoculated arthropods.

A more likely bioterrorism scenario involves malevolent forces utilizing more passive means of compromising U.S. health. North America has many indigenous mosquito species – several of which can spread pathogens found in other parts of the world, such as Rift Valley Fever in Africa. Introduction of any disease capable of spread and maintenance by indigenous arthropods is a significant public health threat. Some unsubstantiated theories suggest West Nile virus was intentionally introduced to the U.S. in this way. Possibilities of an arthropod-facilitated attack has placed a heavy burden on keeping undesirable pathogens out of the country.

There are steps everyone can take to reduce their risk of arthropod-borne diseases. Mosquito control methods, such as elimination of outdoor untreated stagnant water sources, should be practiced regularly. Also, mosquito repellent, in addition to long-sleeved shirts and pants covering the ankles, should be worn whenever going outdoors.

Similar measures can be taken to prevent tick bites – wear repellent, tuck pants into socks or boots, shower after returning indoors, and perform tick checks daily.

The Epidemiologist: Dark Horse of Public Health

By Chris Healey

Many identify physicians as the preeminent professional in the health field – followed by dentists, physical therapists, pharmacists, and nurses – to name a few. However, one of the most important cogs in the health infrastructure mechanization is publicly obscure, yet works almost exclusively with the public. The epidemiologist is the most important health professional you may never meet.

An epidemiologist is not intentionally obscure. The occupation simply does not require as much face-to-face interaction as other health professionals. Instead, epidemiologists analyze data collected by healthcare providers to discern patterns overlooked on a patient-by-patient basis. That data is often analyzed offsite, away from patients. While physicians are treating the individual, epidemiologists are looking at the big picture.

State and federal regulations require physicians and other health professionals to report pertinent diagnosis and patient information to local health departments. That data is collected and analyzed by regional and district epidemiologists to detect unusual disease instances or patterns in their respective regions and districts. Data from local health departments is collected and further consolidated on the state and federal level by state health departments and the Centers for Disease Control respectively.

Epidemiologists serve as the vanguard in outbreak and bioterrorism detection. A clandestine bioterrorism event will likely be detected first by epidemiologists. For example, while several physicians may treat several different E. coli casesin the same day, they are unlikely to communicate mutual diagnoses among themselves. However, an epidemiologist whom analyzes all E. coli diagnoses that day may be able to discern unusual incidence. A physician can identify a single illness, but epidemiologists identify outbreaks and epidemics.

Incidence and pattern detection is only one function of the typical epidemiologist. Once pathogens of interest are detected, epidemiologists investigate patients to determine how they became infected with the respective agent. While physicians can serve in an investigative capacity, diagnosis and treatment of the patient at hand is often their focus. Epidemiologic investigations typically include patient interviews and environmental sample collection. In instances of foodborne illnesses, those investigations are critical to identify the tainted food and water sources. Product recalls and water treatment advisories are often the result of epidemiologic investigations.

Epidemiologists are often marginalized in popular culture and cinema. They are conflated, and often completely replaced, with physicians. However, the 2011 film Contagion portrayed epidemiologists as discrete health professionals with accurate—though dramatized—job functions.

Epidemiology is a growing field. According to the Bureau of Labor Statistics, epidemiologist employment is projected to grow 10 percent from 2012 to 2022, which is about as fast as the average for all occupations.

 

(Image Credit: Contagion)

The Brain-Eating Amoeba and Summertime Activities: What You Need To Know

By Chris Healey

One of the most deadly known organisms on Earth could be lurking in a lake or freshwater source you’ll visit this summer.

Naegleria fowleri is a free-living amoeboflagellate found in warm bodies of water such as ponds, lakes, hot springs, and coastal waters. It is also found in soil, minimally-chlorinated swimming pools, industrial plant water discharge, and water heaters. N. fowleri grows best at temperatures up to 115 degrees Fahrenheit, and survives temperatures in excess of 115 degrees Fahrenheit for a short time.

N. fowleri causes primary amebic meningoencephalitis (PAM), an infection of the central nervous system characterized by brain destruction. The amoeba consumes brain tissue.

PAM occurs when N. fowleri enters the body through the nasal passages, typically when swimming or diving in contaminated freshwater. Once entered through the nose, the amoeba travels to the brain. Early symptoms of PAM are similar to bacterial meningitis and may begin approximately five days after infection.  Initial symptoms include headache, fever, nausea and vomiting. Later, symptoms can include stiff neck, confusion, lack of attention to people and surroundings, loss of balance, seizures, and hallucinations. After onset of initial symptoms, the disease rapidly progresses. Death invariably occurs approximately five days after onset of symptoms.

The fatality rate for an infected person is over 99%. Only 1 out of 128 known infected individuals in the United States between 1962 to 2012 survived infection. In 2011, a 9-year-old child in central Virginia died from the disease.

It is important to note you cannot become infected with N. fowleri by drinking contaminated water. Infection can only occur if ameba-contaminated water enters nasal passageways.

Precautions can be taken to reduce the risk of infection. Avoid swimming in bodies of freshwater during high-water temperatures and low-water levels. Also, refrain from digging in, or stirring up, sediment in shallow areas of freshwater bodies. Those planning on swimming in freshwater lakes should wear a nose plug, hold their nose before diving, or avoid submerging their head. Another effective method is to keep your head above water in freshwater, hot springs, or untreated thermal waters.

A novel infection route involving nasal irrigation was recently reported by the CDC. Those who use a neti-pot, or other nasal irrigation devices, should use discretion when filling their devices.  Water should be boiled for one minute, passed through a 1-micron sized filter, and distilled or sterilized before nasal irrigation use.

 

(Image Credit:  B A Bowen Photography, c/o Wikimedia Commons)

Antibiotic Anomaly: Disparity Between Lawmakers and Health Experts on Antibiotics

By Chris Healey

State lawmakers are working to protect doctors who prescribe antibiotics in excess of recommended guidelines. Those efforts come after the CDC declared antibiotic resistance from antibiotic overuse one of the greatest threats to public health.

The controversy stems from state lawmakers in northeastern states affected by Lyme disease, an amorphous bacterial illness transmitted through tick bites. The Infectious Disease Society of America endorses a four-week antibiotic regimen which they say cures most cases. However, some individuals claim their symptoms persist after the conclusion of antibiotic therapy, a condition called Post Lyme Disease Syndrome.

Individuals reporting Post Lyme Disease Syndrome often harangue doctors for further antibiotic treatment, believing previous treatment was ineffective or inadequate. However, studies on Post Lyme Disease Syndrome indicate persistent infection is unlikely. Instead, lingering perceptions of malaise are likely the result of lasting physiological damage from infection known as sequela. Doctors often resume antibiotic treatment at patient request despite research findings not supportive of continued treatment.

Antibiotics are not harmless therapeutics. They produce negative effects in patients and bacteria alike. Extended antibiotic treatments sometimes lead to severe physiological damage including mitochondrial impairment, aplastic anemia, and Stevens-Johnson syndrome. Unless absolutely necessary, antibiotics should be avoided.

Harm from lengthy antibiotic regimens extend beyond the patient. Prolonged antibiotic exposure allows more opportunity for bacterial selection of respective antibiotic resistance. Bacteria can pass resistance to posterity, complicating treatment in new patients.

A 2013 report released by the CDC served as a call to arms for the medical community concerning the growing threat of antibiotic resistance. The report lists four core actions to stymie resistance. One of the four is improved stewardship – commitment to antibiotic use within established guidelines. The CDC report, and other efforts to increase antibiotic resistance awareness, has placed pressure on health officials to conform to new standards of judicious antibiotic use.

Instead of allowing antibiotic conformity pressure to curb prescriptions, lawmakers have interpreted it as an occupational nuisance in need of remedy. An article in the Wall Street Journal discusses bills in the Vermont and New York state legislature to protect doctors from punishment for over prescribing antibiotics.

There is a clear disconnect between government health officials and state lawmakers. Misguided attempts to protect doctors from antibiotic reform pressures reflect a lack of antibiotic understanding. Health officials must improve efforts to communicate the importance and severity of antibiotic resistance.

No Rabies Treatment After All: Failure of the Milwaukee Protocol

By Chris Healey

Doctors are abandoning the only treatment for rabies.

The Milwaukee protocol, a procedure reported to prevent death after the onset of rabies symptoms, has been performed over 26 times since its inception in 2004 but has only saved one life. Overwhelming failure has lead health officials to label the protocol a red herring.

Rabies is caused by the rabies virus, an RNA-based virus in the genus Lyssavirus. Transmission typically occurs when virus-laden saliva from a rabid animal enters a wound or mucous membrane. Infection typically occurs from a rabid animal bite. The virus travels along peripheral nerves until it reaches the brain and salivary glands. A characteristic rabies symptom is aversive behavior toward water or water consumption called hydrophobia. Individuals demonstrating hydrophobia will generally avoid water and resist drinking it. Other symptoms include anxiety, nerve pain, itching, impaired sensation of touch, convulsions, paralysis, and coma. Cases among unvaccinated individuals almost always result in death.


The Milwaukee protocol was conceived in 2004 by a team of medical professionals, led by Dr. Rodney Willoughby, after a 15-year-old girl was admitted to a Milwaukee hospital after a rabies diagnosis.

After consulting with researchers at the Centers for Disease Control and Prevention in Atlanta, the team formulated and implemented a novel procedure. The patient was placed in a drug-induced coma and given an antiviral cocktail composed of ketamine, ribavirin, and amantadine. Considering the theory that rabies pathology stems from central nervous system neurotransmitter dysfunction, doctors hypothesized suppressed brain activity would minimize damage while the patient’s immune system developed an adequate response.

The patient was discharged from the hospital 76 days after admission. She demonstrated speech impediment and difficulty walking during a clinic visit 131 days after discharge. It is unclear how long those conditions persisted. In subsequent years, the patient attended college. She remains the only Milwaukee protocol success.


There has been confusion regarding the efficacy of the Milwaukee protocol. A 2009 report published by Dr. Willoughby in the journal Future Virology described the efficacy and promise of the procedure. In that article, Dr. Willoughby cited two new instances of rabies patient survival following Milwaukee protocol implementation. Those two cases brought the total number of rabies patients saved by Milwaukee protocol procedure to three. However, those survivor reports were rebuked by a 2013 article published in the journal Antiviral Research. That article explicitly states Dr. Willoughby’s claims in Future Virology are misleading because the two patients mentioned actually succumbed to rabies.

Overwhelming Milwaukee protocol failure has been attributed to anomaly in the initial patient. For example, she was bitten by a bat, but that bat was not recovered. Without the bat, it is impossible to test the causative rabies agent to rule out a less virulent variant. A mild version could be fought off more easily and could help explain her survival. Additionally, researchers cannot rule out the possibility the patient possessed extraordinary physiology that somehow impaired the rabies progression.

Health officials claim Milwaukee protocol repetition impedes efforts to find new treatments. Instead of exploring new techniques, doctors fall back on the Milwaukee protocol because it was once successful. Crushing failure has prompted the health community to place a taboo on the protocol, encouraging experimentation that may lead to different treatment options.

 

Image Credit: CDC

Airborne Bird Flu Transmission: Balancing Scientific Recourse and National Security

By Chris Healey

Articles recently published in the scientific journal Cell mark the end of a long battle for one researcher in his endeavor to publish research that raises security concerns.

Ron Fouchier, a virologist with Erasmus University Medical Center in the Netherlands, published an article in Cell explaining how H5N1, the causative agent of bird flu, can be genetically modified for airborne transmission between mammals. Dr. Fouchier says his research can help prevent bird flu pandemics. However, others in the scientific community believe Dr. Fouchier will cause what he seeks to prevent.

David Relman, a researcher at Stanford University, says Dr. Fouchier is essentially giving would-be terrorists instructions on how create a deadly contagion.


The controversy began in December 2011 when the  National Science Advisory Board for Biosecurity (NSABB), a federal advisory committee composed of twenty-five members who provide expertise in areas such as molecular biology and infectious diseases, advised all scientific journals to refrain from publishing Dr. Fouchier’s H5N1 airborne transmission research.

In February of 2012, the World Health Organization released its own evaluation of the research. The WHO stated Dr. Fochier’s work had scientific value and should be shared in its entirety. Shortly after the WHO’s report, the NSABB reevaluated the research findings. In March 2012, it retracted its recommendation to refrain from publishing. The complete study, along with all its findings, was finally published in Cell on April 10, 2014.

By its nature, science is a cumulative process. Communication among professionals is essential to promote progress and mutual understanding. Experts agree scientific advancement progresses best when least inhibited by authority. Government intervention generally pushes great minds away from heavily-scrutinized areas into those less regulated.

However, national security remains a priority and precedent exists for controlling scientific literature. The Atomic Energy Act of 1946 was passed to control and restrict nuclear weapons research conducted in the United States during WWII. No similar legislation exists to prevent communication of biological findings. However, the government can take steps to restrict research with dual use findings.

Government information classification, colloquially known as identifying information as top secret, secret, or confidential, is useful for keeping government-owned information away from the public. However, research the government had no part in creating, either through federal funding or conducted by government employees cannot be given a sensitivity label.

A common practice in government funding of scientific research is the requirement of funding to be contingent upon acceptance of sensitive but unclassified contract provisions. Those provisions allow the government to have authority on whether research findings can be published.

Dr. Fouchier’s research was precarious because it was conducted in a foreign university but supported by U.S federal funds. Outside the United States, the federal government has less control over research conducted under its auspices. It is unclear if Dr. Fouchier’s research was subject to a sensitive but unclassified contract provision.

With the power of the purse, the federal government can influence research and publication decisions through threat of funding withdrawal. While federal money funds much scientific research, simply pulling funding is not a fool-proof censorship method. Private benefactors can step in for lack of government support. The government can wield no financial influence on those sources receiving no government funding, including research funded by foreign governments.

Outside of financial influence, the government can best stop publication of sensitive material through NSABB recommendation. The committee has many ties to scholarly publications and is generally well respected. Initial recommendations not to publish Dr. Fouchier’s research were very influential; it was not published until well after committee approval.

There is no straight-forward answer to questions concerning science and security dissidence. Benefits of sharing scientific research must be weighed with harm that could arise from that research.

 

Image Credit: James Jin/Flickr

Dirty Bombs: An Enigma of Identity and Non-use

By Chris Healey

Radioisotopes can be used to construct radiological weapons. The United Nations reported 140 cases of missing or illegally-used radioisotopes in 2013. Each instance represents a potential threat to safety and security.

Radiological dispersal devices, or dirty bombs, are mundane. They do not deserve the mystique commonly associated with the term. Dirty bombs require little technical expertise to assemble and detonate. Radioisotopes, the defining component in dirty bombs, are abundant. A radioisotope is any unstable element that releases matter or energy. They can be found in common occupational tools such as well-logging and medical diagnostic equipment, and in household items such as smoke detectors.

Components required to create dirty bombs consist of conventional explosives, detonation apparatuses, and radioactive isotopes. Design simplicity makes dirty bombs accessible to those with little or no technical knowledge. In contrast, biological and chemical agents require expertise to create viable weapons. Complexity serves to complicate production processes, thereby limiting creation success rates.

Simple construction and abundant components make dirty bombs an attractive attack method. Surprisingly, they are rare. According to data from the Radiological and Nuclear Non-State Adversaries Database, dirty bombs, and other radiological weapons, have only been used 19 times by non-state actors.

Radiological and nuclear weapons are often conflated. Nuclear weapons employ physical processes of fusion or fission to release massive amounts of energy. Fission is the process of splitting an atom. That process yields smaller atoms, neutrons, and energy. Fusion is the process of combining two atoms to create one, yielding energy. Both processes require extraordinary and precise conditions for realization. Fusion and fission expel devastating amounts of energy, tantamount to the detonation of thousands to millions of tons of TNT. Furthermore, both fission and fusion require rare radioactive isotopes, profound scientific expertise, and expensive equipment. The cost and technical nature associated with fusion or fission make device creation insurmountably difficult. Conditions to create fusion and fission contrast sharply with dirty bomb detonation requirements.

Conventional explosives spread radioisotopes upon detonation.  Radioisotopes retain radioactivity after blasts, contaminating surrounding areas with radiation. Conventional explosives are incapable of producing fusion and fission reactions. Nuclear weapons and dirty bombs share only the ability to spread radioactive material. However, destructive abilities of the two weapons cannot be compared; dirty bombs are exceedingly insignificant in comparison to nuclear weapons.

Other than the conventional explosive blast, inhalation of dispersed radioactive debris is the greatest health threat of dirty bombs. In almost all cases, radiation dispelled by dirty bombs will be stochastic instead of deterministic. Stochastic radiation damage does not immediately harm the individual, but may lead to carcinogenesis months to years later. In other words, the health effects of dirty bomb debris will manifest long after an attack. Deterministic damage, often associated with nuclear weapons, causes harm hours to weeks after radiation exposure. It is associated with deterioration of radiation-damaged organ tissue, not cancer.

Dirty bomb non-use cannot be explained. However, every effort must be made to improve radioisotope accountability. Restricting unauthorized radioisotope access will decrease radiological attack opportunities.

 

Image Credit

Bioscavengers: The Ultimate Defense Against Nerve Agents

By Chris Healey

Bioscavengers are naturally-occurring proteins capable of effective nerve agent elimination. They are currently theoretical or in the early stages of clinical trials. However, they have the potential to revolutionize the prevention of nerve agent poisoning.

Discovered by German chemists researching insecticides in the 1930s, nerve agents were quickly recognized as a potential weapon. Nerve agents were produced and stockpiled by the Germans during World War II but were never used. Their first use during wartime occurred during the Iraq-Iran conflict in the 1980s. Iraq reportedly released nerve agents against Iranian troops and later against members of its Kurdish population.Nerve agents were recently used during Aum Shinrikyo’s Tokyo subway attack in 1995, and again in 2013 by the Assad regime during the Syrian Civil War.

The nervous system controls muscle contraction through release of neurotransmitters into neuromuscular junctions, which are media between neurons and muscle fibers. Acetylcholine is the primary neurotransmitter involved in muscle contraction.

Nerve agents bind and inactivate acetylcholinesterase, a regulatory protein of acetylcholine within neuromuscular junctions, thus preventing acetylcholine dismissal. Acetylcholine accumulation leads to salivation, sweating, abdominal cramps, muscle twitching, and flaccid paralysis. Death occurs from inadequate respiratory function as a result of neuromuscular junction disruption in the diaphragm.

Distinguishing prophylaxis from pretreatment is important in nerve agent countermeasure discussion. Pretreatment is any therapy administered before poisoning so that treatment after poisoning can be more effective. Prophylaxis is pretreatment that does not require additional intervention. In other words, prophylaxis eliminates the need for treatment after poison exposure.

The necessity of pretreatment limits the efficacy of conventional nerve agent treatments. Nerve agents rapidly cause irreversible damage within neuromuscular junctions. The presence of a pretreatment such as pyridostigmine, an acetylcholinesterase inhibitor, helps minimize damage before post-exposure treatment can be administered.

Atropine and oximes—post-exposure treatments for nerve agents—have limited efficacy. They are toxic if administered in the absence of nerve agents. Furthermore, they must be administered very shortly after nerve agent exposure to have any therapeutic effect. If administered following a pretreatment, and in a timely manner after nerve agent exposure, atropine and oximes can prevent death. Incapacitation, convulsions, and long-term neurologic damage, however, are unavoidable despite treatment.

Bioscavengers function as a prophylaxis. Damage to neuromuscular junctions only occur in the presence of nerve agents. In other words, bioscavengers eliminate the need for atropine and oximes, while nullifying any chance of long-term neurologic damage.

Although everyone possesses trace amounts of bioscavengers in their bloodstream, innate levels are too minute to ward off physiologically-significant nerve agent quantities. Bioscavengers must be extracted from enormous amounts of human plasma and administered in a concentrated regimen to counter nerve agent exposure. Harvesting bioscavengers from plasma is costly, inefficient, and impractical as a means of production. More efficient production methods, such as harvesting molecules from the milk of transgenic goats, are currently under investigation.

Current bioscavengers are considered stoichiometric, meaning each bioscavenger molecule can only eliminate one nerve agent molecule. To be effective, there must be enough stoichiometric bioscavengers in the bloodstream to eliminate the amount of nerve agent concurrently present.

The prophylactic nature of bioscavengers, compounded with the rapid effect of nerve agents, render them useless if administered after nerve agent exposure. Strict use as a prophylaxis limits therapeutic utility. For example, it would be impossible to administer bioscavengers to victims of a terrorist attack involving nerve agents prior to the event. However, bioscavengers would be extremely valuable to first responders as they potentially expose themselves to nerve agents in that situation. Furthermore, soldiers and others in war zones anticipating a nerve agent attack could administer bioscavengers to proactively neutralize that threat.

A catalytic bioscavenger is a theoretical concept that improves upon stoichiometric limitations by exploiting enzymatic behavior. Instead of a one-to-one ratio, whereby a bioscavenger eliminates itself by binding to a nerve agent, catalytic bioscavengers would be capable of eliminating many nerve agents over time. In other words, catalytic bioscavengers would not only be able to eliminate large amounts of nerve agent during a single exposure, but would also maintain functionality through multiple exposures. Catalytic bioscavengers would eliminate therapeutic re-administration for continued nerve agent protection following initial exposure. While enzymatic utility may be frivolous for use in first responders, that function would be advantageous to those in situations involving multiple nerve agent attacks.

Methods to create catalytic bioscavengers are under investigation. Researchers are studying the protein structure of stoichiometric bioscavengers to see how it can be altered to form an enzyme. Once appropriate alterations to its chemical composition have been identified, genetic instructions can be created to produce desired results in a transgenic organism.

Ebola: a pandemic of misconception

By Chris Healey

An  Ebola hemorrhagic fever outbreak in the Republic of Guinea has raised concerns about the illness and its spread to countries outside Africa.

Ebola is a virus in the filoviridae family. Of the five Ebola species, only Zaire, Sudan and Bundibugyo species have caused outbreaks in humans.

Ebola appears to be an incidental host of humans from a natural cycle involving bats and nonhuman primates. Humans enter the cycle after contact with blood and tissue from nonhuman primates, often after instances of butchering and animal cruelty. Transmission routes from bats to humans are possible but currently unknown.

The first confirmed outbreak of Ebola occurred in 1976 in Nzara, a small town in southern Sudan. Workers from a local cotton factory spread the disease to their relatives and others in the community. The outbreak lasted several months. Of the 284 cases in that outbreak, 151 died.

Ebola causes Ebola hemorrhagic fever, a severely debilitating illness affecting multiple organ systems. Ironically, hemorrhage is an uncommon symptom reported in fewer than half of all cases. Death typically occurs due to shock from fluid loss and organ failure.

Mortality rate is species dependent. Bundibugyo has a 36% fatality rate, Sudan 55%, and Zaire 90%. There is no cure, but administration of an experimental vaccine that targeted a viral protein used for attachment and entry to the host cell was attributed to the survival of an accidentally-exposed laboratory researcher in Germany.

Ebola has been the inspiration for fictional literature and film. The Hot Zone by Richard Preston provides an overview of Ebola and other filoviruses before focusing on the discovery of Reston Ebola, a species known to only sicken nonhuman primates, in Reston, Virginia. The 1995 movie Outbreak featured an Ebola-like virus as the primary plot device.

Both works exaggerate Ebola hemorrhagic fever’s morbidity and hemorrhagic symptoms to inflate pathogenicity and pandemic potential. While there is no denying the severity of Ebola hemorrhagic fever illness, it is an ineffective cause of pandemics.

Perhaps the most misunderstood characteristic of Ebola is its method of transmission. Direct physical contact with infected persons or their bodily fluids is required to transmit the illness. There is no evidence of airborne transmission among Ebola species known to affect humans. Ebola rapidly becomes nonviable outside the host when aerosolized in uncontrolled, non-laboratory settings.

Ebola has an incubation period of 4 to 10 days. Rapid onset allows healthcare providers to quickly identify affected individuals. Only symptomatic individuals can spread the disease. In other words, the disease cannot be transmitted during incubation or through non-symptomatic cases. A short, non-communicable incubation period limits Ebola’s pandemic potential.

Limitations of direct person-to-person spread can assist public health response efforts in the event of an Ebola hemorrhagic fever outbreak. Quarantine procedures are effective in restricting the illness shortly after detection. Due to the lack of airborne transmission, direct contacts with sickened individuals can be traced and contained, arresting illness progression. Ebola hemorrhagic fever rarely escalates past a localized outbreak if adequate public health infrastructure is present.

Media consumers should be wary of fictional or exaggerated portrayals of illness. The media’s tendency to misuse and dramatize information can breed undue fear in the event of a public health crisis.

Reemergence of smallpox: A greater threat now than ever before

By Chris Healey

In the event of a resurgence of smallpox, treatment and containment would be exacerbated by illnesses and medical practices not present when the virus was eliminated.

Smallpox was one of the most significant diseases in human history. Although it was first distinguished from measles in China around 340 AD, evidence of the disease has been found on the remains of Egyptian mummies entombed over a thousand years earlier.

Smallpox is caused by Variola major, a virus in the Orthopoxvirus genus. The illness is known for causing characteristic pustules, severe symptoms and debilitating morbidity. Mortality rates exceeding 30% have been reported. The disease is almost always fatal in immunocompromised individuals.

Efforts to confer immunity against smallpox have been practiced for centuries. A technique called variolation, which involved inoculation with material from smallpox pustules, was used as far back as 1000 AD.

Due to the conserved nature of Orthopoxvirus, immunity to a wide range of viruses within the genus can be conferred after infection with a virus within the same genus. In 1796, Edward Jenner discovered inoculation with cowpox conferred immunity to smallpox. He called the technique vaccination, from the Latin vacca for cow. Vaccination results in less adverse effects and fatalities than variolation, making it the preferred method of conferring smallpox immunity.

Today, vaccinia virus is used in lieu of cowpox virus to confer immunity. Vaccinia virus creates a localized lesion that disappears over time in most individuals.

Persistent vaccination practices lead to the elimination of smallpox from most industrialized countries by the 1950s. In 1966, the World Health Assembly voted to fund an aggressive worldwide vaccination campaign to whittle away remaining pockets of the illness. After a successful campaign, the World Health Organization declared smallpox eradicated on December 9, 1979. The organization issued a recommendation for the cessation of smallpox vaccination in 1980.

Although smallpox is not a public health threat, it still exists. Stockpiles of the virus are maintained at the headquarters of the Centers for Disease Control in Atlanta and at a biotechnology institute in Novosibirsk, Russia.


Reintroduction of smallpox to the population would be devastating. Several immunologically-naïve generations are present. Other than those who received smallpox vaccines through military or specialized research positions, the entire population is almost completely unprotected.

Immunocompromised individuals who receive a vaccine utilizing a virus capable of self-replication, also known as a replication-competent vaccine, have a risk of developing a condition called progressive vaccinia. It is an extremely debilitating condition with no cure and a 90% fatality rate.

Dryvax, the vaccine used to eliminate smallpox, was replication-competent. Progressive vaccinia was reported as a rare adverse reaction when smallpox vaccines were administered during eradication efforts. Although Dryvax is no longer used, another replication-competent vaccine, ACAM2000, has taken its place. If ACAM2000 is administered to the general population today, far more cases of progressive vaccinia are expected to occur.

HIV and immunosuppression drugs are two modern factors contributing to decreased immune function. The World Health Organization estimates 35.3 million people in the world are living with HIV—1.1 million of those in the United States. Immune suppression associated with the illness would make smallpox vaccination undesirable, and smallpox infection fatal. HIV was not a factor during eradication efforts. Individuals with HIV would be at great risk in the event of smallpox reemergence.

Many modern drugs dampen the immune system to alleviate a range of conditions and symptoms, from hay fever and asthma to anti-rejection drugs for transplant recipients. Immunosuppression drugs have become commonplace. Those drugs did not play a significant role during eradication efforts because they were very expensive and uncommon. In the event of a re-emergence, smallpox would likely exploit those taking immunosuppression drugs. Furthermore, immunosuppression drugs dramatically increase the chance of developing progressive vaccinia following smallpox vaccine administration.

There is, however, a vaccine alternative for immunocompromised individuals. Imvamune is a replication-incompetent vaccine produced by Bavarian Nordic. Replication-incompetent vaccines deliver a virus incapable of replication, meaning it cannot cause progressive vaccinia. Unfortunately, there is no way to test the vaccine’s ability to confer smallpox immunity. Replication-incompetent vaccines are generally considered by health experts to be less effective at conferring immunity than replication-competent alternatives.

It is for these reasons that the re-emergence of smallpox would deal a catastrophic blow to the wellbeing of individuals around the world and therefore every effort must be made to prevent the return of smallpox.