Ebola Epidemic: Fearbola

Aliases: Ebola hemorrhagic fever, Ebola virus disease, EVD, Ebola

Ebola virus disease (EVD) is one of the most virulent illnesses in the world, and the current outbreak is the largest ever recorded. As of July 30th, the Ebola epidemic had spread to include 4 countries in West Africa (Guinea, Liberia, Sierra Leone, and Nigeria), and there had been 1440 suspected and confirmed cases and 826 suspected case fatalities, amounting to a fatality rate of about 57%3 (for the latest update, here is the CDC outbreak site). In light of the seriousness of the situation, I thought it time for an exploration of the facts about this epidemic and the disease itself.

Where does Ebola come from?

Ebola outbreaks have occurred in waves since the disease was first identified in 1976 in the Democratic Republic of Congo, near the eponymous Ebola River1,3. While several animal species can carry the virus (see the Cause section below), they are thought to be accidental hosts, like humans. Although the natural host and disease reservoir remains unclear3, it currently considered to be fruit bats in the Pteropdidae family1. There are 5 species of Ebola virus, only 4 of which cause disease in humans1,3. The species vary widely in severity, with case fatality rates ranging from about 25% to 90%.

Why is this outbreak so bad?

The current Ebola epidemic is of the most lethal species, but that isn’t the only reason it has been so difficult to control. This is the first outbreak to occur in the affected region of West Africa, and medical professionals there were largely untrained for an Ebola epidemic. They were also short-staffed; there was a shortage of health workers on the ground. Most previous epidemics have happened in more rural areas, whereas this outbreak has struck fairly urbanized regions. With greater infrastructure comes greater travel, and people are better able to move the disease long distances, making potential cases harder to track2.

Fear has aided the disease. The belief that health workers are spreading the illness has made people unwilling to report cases. Relatives are also hesitant to report their loved ones for fear that they will be taken away to die alone. Compassion and cultural practices have also played a role; the care of sick relatives and funeral practices put the healthy at risk2.

Fear of the epidemic spreading to North America has ratcheted up with the return of Dr. Kent Brantly, an American aid worker, to the US for treatment after he contracted Ebola in Liberia. The CDC has been quick to nip these concerns in the bud, reiterating that 1. Ebola is not airborne, 2. Ebola is not waterborne, and 3. Ebola is controllable in US healthcare settings.

ebola epidemic
Mugshot.

Cause: EVD is (re)introduced into human populations through close contact with the bodily fluids of infected animals (this can include gorillas, chimpanzees, monkeys, fruit bats, forest antelope, and porcupines). It is then transmitted from person to person by direct contact (through broken skin or mucous membranes) with the bodily fluids, such as blood, secretions, or semen, of an infected person. It may also be transmitted indirectly, through contact with a contaminated environment. Recovered patients can remain infectious long after they return to good health; the virus has been found in the semen of male patients up to 61 days after recovery1.

Consequence: After an incubation period (the time from exposure to the onset of symptoms) of 2 to 21 days, patients will initially experience fever, extreme weakness, headache, muscle pain, and sore throat. As the disease progresses, the sick will develop a rash, diarrhea, vomiting, impaired kidney and liver function, reduced white blood cell and platelet counts, and, in the most extreme cases, internal and external bleeding1.

Cure: There is no vaccine or treatment for EVD. Outbreaks are controlled using quarantine and other transmission prevention measures1,3.

References

1. Ebola virus disease. World Health Organization. April 2014. Web. 3 August 2014. http://www.who.int/mediacentre/factsheets/fs103/en/

2. Osterholm, MT. “Why it’s harder to contain this Ebola epidemic”. Chicago Tribune. 4 August 2014. Chicagotribune.com. Web. 3 August 2014.

3. Outbreak of Ebola in Guinea, Liberia, Sierra Leone. Centers for Disease Control and Prevention. 3 August 2014. Web. 3 August 2014. http://www.cdc.gov/vhf/ebola/outbreaks/guinea/index.html

Image source: Creative Commons, http://ceb.wikipedia.org/wiki/Pteropodidae

Pulmonary Embolism: A Special Request

Aliases: pulmonary embolism, PE, venous thromboembolism

Because this is a special, themeless post, I decided to cut to the chase and talk about what I imagine people really want to know when they’ve been diagnosed with pulmonary embolism (PE): what will my life be like now? Within the medical community, quality of life (QoL) is defined as the “patients’ recorded impact of disease and treatment on his/her physical, psychological and social functioning and wellbeing”4. While the biological impact of PE is relatively concrete and can be conveniently assessed statistically, the social and psychological effects are subjective and consequently much harder to measure.

The clinical component of QoL is relatively straightforward and, in this case, fairly positive. The recurrence and mortality rates after diagnosis are low. PE-related mortality is less than 2% during the typical 3-6 month anticoagulant/thrombolytics treatment period following a PE, and remains fairly steady (rising to 2.7%) over the course of 3.1 years. The risk of recurrent PE is higher: around 6% during the first 6 months after diagnosis, and rising to a cumulative recurrence rate of between 29.1-34.5% (depending on the study) over the following 10 years. When recurrent PE occurs, it has an estimated case fatality rate of between 10-45%. However, this is very likely an overestimate, because autopsies are rarely conducted when recurrent PE is suspected as the cause of death. More likely than recurrence are related complications, such as residual perfusion defects, which affect 31.4% of PE patients within the first 12 months after their diagnosis2.

The social and psychological effect of PE, its impact on the patient’s perception of their wellbeing, is much more varied1, but there are some fairly consistent trends. While overall QoL for PE patients is lower than healthy control groups, it is significantly higher across the board than patients suffering from chronic cardiovascular diseases, specifically chronic obstructive pulmonary disease (COPD) and congestive heart failure. PE’s long-term impact is similar to other acute cardiovascular disorders; the QoL for PE patients is roughly equal to that of acute myocardial infarction (aka heart attack) patients. Finally, the best news: it gets better. The further from the diagnosis, the higher PE patients rated their QoL4.

pulmonary embolism
It’s all relative.

Cause: PE is caused by material, usually a blood clot, lodging in one or more pulmonary arteries, blocking blood flow to lung tissue. These clots almost always travel to the lungs from the legs and are often the result of deep vein thrombosis (DVT), a condition where a blood clot forms in a vein deep in the body. While anyone can develop DVT and PE, several factors increase the likelihood of their occurrence. Surgery, especially hip and knee replacements, are a leading cause, because they may introduce tissue debris into the bloodstream, and require immobility both during and after the procedure. Other risk factors include a family history of blood clots, heart disease, or certain cancers, as well as prolonged immobility (e.g. bed rest), being overweight, pregnancy and smoking. Unfortunately, one bad turn can beget another; once a person has had one embolism he or she has a greater risk of having another3.

Consequence: The most common symptoms of PE are a sudden shortness of breath that gets worse with exertion, chest pain, reminiscent of a heart attack, that may increase with coughing, breathing deeply, or bending over, and coughing that may produce bloody sputum. Other symptoms include leg pain or swelling, clammy or discolored skin, rapid or irregular heartbeat, dizziness, and excessive sweating. However, the symptoms of PE are highly variable, and depend on the size of the clots (there are almost always more than one), how much of the lung is affected, and the how healthy the person was before the PE3.

Cure: Treatment is critical for pulmonary embolism; approximately 1/3 of untreated patients will die. Because PE can be difficult to diagnose, physicians generally use multiple approaches, including blood tests for clotting factors, and a variety of body scans (e.g. x-rays, CT scans, or an MRI). Once it has been identified, PE is treated by either breaking down the blood clot with anticoagulants (blood thinners) and thrombolytics (clot dissolvers) or removing the clot surgically, or both. In extreme cases, PE is treated with an implanted vein filter that prevents blood clots from reaching the heart and lungs3.

References

1. Hogg, K, M Kimpton, M Carrier, D Coyle, M Forgie, & P Wells. (2013). Estimating quality of life in acute venous thrombosis. Journal of the American Medical Association Internal Medicine, 173(12).

2. Meyer, G, B Planquette, & O Sanchez. (2008). Long-term outcome of pulmonary embolism. Current Opinion in Hematology, 15:499-503.

3. Pulmonary embolism. Mayo Clinic. 2 January 2014. Web. 11 April 2014. http://www.mayoclinic.org/diseases-conditions/pulmonary-embolism/basics/definition/con-20022849

4. van Es, J, PL den Exter, AA Kaptein, CD Andela, PMG Erkens, FA Klok, RA Douma, ICM Mos, DM Cohn, PW Kamphuisen, MV Huisman, & S Middeldorp. (2013). Quality of life after pulmonary embolism as assessed with SF-36 and PEmb-QoL. Thrombosis Research, 132:500-505.

Image source: http://integral-options.blogspot.com/2012/02/pierre-cote-relative-happiness-index.html