EbolaFast-spreading killers: how Ebola compares with other diseases
The West African outbreak of Ebola has claimed more than 4,800 lives and this number is sure to rise. There is understandably a lot of fear about Ebola, but how does it actually comp re with other fast-spreading infectious diseases? While bubonic plague is bacterial, all of the other infections mentioned below – influenza, Bird Flu, SARS, Ebola, and HIV/AIDS — are viral. Yellow fever was the first human virus to be discovered in 1901. Since then more than 200 have been recognized. Ebola has all the epidemiological characteristics of a containable infection, but it is only now spreading to developed countries that have no experience of dealing with it. The desirable strategy, from global health and humanitarian perspectives, is to eliminate the epidemic at its source.
Massey University's Mick Roberts // Source: massey.ac.nz
The West African outbreak of Ebola has claimed more than 4,800 lives and this number is sure to rise. There is understandably a lot of fear about Ebola, but how does it actually compare with other fast-spreading infectious diseases?
Bubonic plague
Plagues have been reported since biblical times, but it is difficult to know how serious these early epidemics were, or even what the infectious agent was.
We now know that plague is a serious disease caused by the bacteria Yersinia pestis. The Black Death is thought to have been bubonic plague, named after the presence of infected lymph nodes; it killed one-third of the population of Europe in the fourteenth century. Bubonic plague killed one-quarter of the population of London in 1563, and the Great Plague of London killed 100,000 a century later.
Plague is spread by fleas that usually infest rodents. The disease is still found in parts of Asia, Africa and the Americas. Few humans are now infected, although outbreaks occasionally occur. The extensive wildlife reservoir means that it will never go away.
The plague: a profile
- Region: China
- The first recorded pandemic was the Justinian Plague, which began in 541 AD
- Origin: Infected rodents, black rats, and fleas
- Infection agent: Bacteria (Yersinia pestis)
- Transmission medium: Infected rodents and fleas Plague affects rodents, such as rats. People are most commonly infected by being bitten by a flea that is infected with the plague bacteria. The pneumonic form of the plague can be transmitted by cough droplets.
- Incubation: 2-6 days. Someone infected through the air could become ill within 1 to 3 day.
- Transmission rate: Rc of 1.3 for pneumonic plague (Ro([basic reproduction number] is an approximate measure of how many new infections one person will generate during their infectious period).
- Fatality rate: 8-10% (It was over 60% pre antibiotics)
- Death toll: Over 100 million deaths
- Medication status: no vaccine.Plague vaccines are in development but are not expected to be commercially available in the immediate future.
Source: WHO & CDC
Influenza
The 1914-18 war resulted in between fifteen and eighteen million deaths, but the 1918 flu pandemic killed more than twice that number.
Influenza spreads rapidly by coughs and sneezes which release small droplets. These droplets may infect others while airborne or by contaminating surfaces.
