See How Ebola’s Spread Compares to Other Deadly Outbreaks

When the director of the Centers for Disease Control and Prevention (CDC) compared Ebola to AIDS last week, he introduced a new note of urgency to the outbreak. As was the case in the early days of HIV, there are currently no approved drugs to treat Ebola, and the virus carries the potential to cause untold devastation—not to mention a lot of panic.

But as an epidemic, Ebola has far more in common with other diseases. Here’s a comparison of Ebola’s impact over the past 19 weeks to other recent outbreaks that, like Ebola, have no known cure or vaccine.

Middle East Respiratory Syndrome (MERS)

MERS is a viral respiratory illness first reported in Saudi Arabia in September 2012. The World Health Organization has since reported 853 MERS infections, of which at least 301 were fatal, as of Sept. 30, 2014. Close contact seems to spread MERS, but it’s unclear exactly how the infection travels.

Severe Acute Respiratory Syndrome (SARS)

The 2003 SARS outbreak in Hong Kong lasted nine weeks before flatlining, but spread far faster than Ebola. SARS is transmitted more easily from person to person, often from an infected person’s coughs and sneezes. The Ebola virus is not considered airborne because larger droplets of bodily fluids are required for transmission. Over 8,000 cases were reported, with a 10 percent fatality rate. SARS was effectively contained after two months.

Marburg Virus

The Marburg virus, named after the city in Germany where it was discovered, belongs to the same family of viruses as Ebola, which cause severe internal bleeding. And like Ebola, human-to-human transmission occurs through close contact with blood or other bodily fluids, often infecting family members and health care workers. The most recent widespread outbreak of Marburg, in Angola in 2005, lasted 26 weeks and caused 374 infections and 329 deaths.

HIV, by contrast, spreads far slower. There is not comparable data for the first weeks of the HIV pandemic.

For outbreaks with no known cure, response teams seek to halt transmission through patient isolation and careful tracing of an infected person’s contact with others. With over 8,000 infected, containment of Ebola poses a greater challenge than similar outbreaks in recent history.

Methodology

Data compiled from periodic World Health Organization updates for Ebola, Marburg, SARS and MERS.