Could Ebola rank among the deadliest communicable diseases?

About 10 million people around the world died of communicable diseases in 2010, the most recent year for which fully comparable international figures are available.

There were no Ebola outbreaks that year; in fact it was the only year since 2007 without an outbreak.

The current Ebola outbreak in West Africa has already claimed over 4,700 lives.

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Last week, the World Health Organization projected that by Dec. 1, the number of new Ebola cases in Guinea, Liberia and Sierra Leone would be 5,000 to 10,000 per week. Even at the low estimate, that could result in a death rate on an annualized basis that would put Ebola at the number six spot on the list of deaths from communicable diseases around the world.

This is calculated by factoring in the U.S. Centers for Disease Control and Prevention view that the number of actual cases of Ebola is about 2.5 times what gets reported to the WHO. 

Looking at the numbers another way, if the current Ebola outbreak were to continue for at least another six months beyond December at 10,000 new cases per week, it also could be at the number six rank. Previous outbreaks did not last that long. 

However, the current Ebola epidemic is not only the worst in terms of infections and deaths, it is also the longest lasting. But Dr. Bruce Aylward, WHO Assistant Director-General, says their goal is to begin to slow down the outbreak by early December.

No. 1 communicable disease

The number one killer when it comes to communicable diseases are lower respiratory infections, especially pneumonia. About 2.8 million people died from LRIs in 2010, about half of them children under five years old.

HIV/AIDS is number two, but it is responsible for only about half as many deaths as LRIs. HIV was the number seven deadliest communicable disease in 1990 but deaths grew and peaked in 2005, at about 1.7 million, before falling to about 1.3 million a year by 2013, according to the Institute for Health Metrics and Evaluation at the University of Washington. The IHME website hosts the Global Health Data Exchange.

The number of deaths from diarrheal diseases fell by 42 per cent from 1990 to 2010, but it is still at number three worldwide.

By comparison, deaths from lower respiratory infections declined 18 per cent during those decades, while tuberculosis, at number four, declined 17 per cent.

The WHO estimates that one-third of the world's population have been infected by the bacteria that causes TB but are not ill with the disease, at least not yet. Over 95 per cent of deaths from TB happen in developing countries.

More people now dying from Ebola each week than malaria in Guinea, Liberia, Sierra Leone

Death from malaria, the fifth deadliest communicable disease, grew rapidly from 1990 to 2003, with an estimated 1.2 million deaths that year.

Africa was responsible for that increase, as "outside of Africa, malaria mortality has been steadily decreasing since 1990," the IHME says.

The average age of death from malaria is 15. By comparison, it's 39 for HIV/AIDS and 53 for TB.

Since 2004, child deaths from malaria in sub-Saharan Africa decreased by 31.5 per cent, the IHME estimates. The death toll from malaria was about 855,000 in 2013.

The IHME notes that "there is massive uncertainty around these estimates," as there is for other diseases. 

In the three countries where Ebola is now epidemic, Guinea, Liberia and Sierra Leone, there were about 27,000 deaths from malaria, or 512 per week on average in 2013. In those three countries, the combined death toll from Ebola for the week ending Oct. 12 was 614.

Top 5 account for 80% of all deaths from communicable diseases

The top five account for about 80 per cent of all deaths from communicable diseases.

For children under five years, about half the deaths in 2013 were from infectious diseases, according to a study published in The Lancet this month. Pneumonia, diarrheal diseases and malaria rank as the leading infectious causes.

Deaths from some of the next ten diseases on the chart have dropped dramatically from 1990 to 2010. For example:

• Measles, down 80 per cent.
• Syphilis, down 44 per cent.
• Tetanus, down 78 per cent.

At the same time, two of the three types of hepatitis are up significantly. Hepatitis B deaths rose 90 per cent and hepatitis E, 56 per cent, while the deaths from hepatitis A fell just 2 per cent between 1990 and 2010. The types of hepatitis are caused by different viruses, but all affect the liver.

Leishmaniasis, despite being at number 15 on the list, rarely gets news coverage in Canada. It's a parasitic disease spread by sand fly bites. It is also treatable and curable, despite the high death toll. According to the WHO, Leishmaniasis "affects the poorest people on the planet, and is associated with malnutrition, population displacement, poor housing, a weak immune system and lack of resources."

The number one cause of death on the planet is not a communicable disease but coronary artery disease, which leads to heart attacks. Strokes are number two.

Source: Institute for Health Metrics and Evaluation

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