I realized that I didn't know very much about how previous flu-like pandemics have spread in Africa. So I looked up a bunch of maps! Blog post here, thread to follow. (N.B. not an epidemiologist, not making claims about how COVID-19 might spread) /1 rachelstrohm.com/2020/03/14/wha…
I started w/ Wikipedia's list of flu pandemics, added SARS and seasonal flu. en.wikipedia.org/wiki/Influenza… The three post-2000 pandemics are coronavirus (2020), H1N1 / swine flu (2009), SARS (2003). /2
Here's coronavirus as of 12 March 2020. Map source: foreignpolicy.com/2020/03/04/map…. Few cases in Africa, lots of debate over why (newscientist.com/article/223676…). Possibilities: little air traffic (en.wikipedia.org/wiki/Civil_avi…), improving public health systems (thinkglobalhealth.org/article/africa…). /3 
Here's H1N1 / swine flu in 2009. This was less severe than coronavirus, more like the seasonal flu. Relatively few African cases. Map source: en.wikipedia.org/wiki/2009_flu_… /4
Here's severe acute respiratory syndrome (SARS) in 2003. This virus had much more severe symptoms, so it was easier to identify the people who were sick & stop the spread. Very few African cases. Map source: theglobalist.com/china-coronavi… /5
What about the seasonal flu in recent years? This looks rather different. This map averages data from 2011 - 2016. Flu occurs year-round in many African countries. Map source: researchgate.net/figure/Global-… /6
I was surprised b/c I'd heard little about flu in Africa. Turns out that surveillance data is weak, and most countries don't have annual vaccines. ncbi.nlm.nih.gov/pmc/articles/P… It's also possible that flu is misdiagnosed as malaria, which is endemic. thelancet.com/journals/langl… /7
What about older flu-like pandemics? We might expect them to spread differently b/c of changes in air travel patterns. Wikipedia lists 4 from 1900 - 2000: Russian flu (1977), Hong Kong flu (1966), Asian flu (1957), and Spanish flu (1918). /8
I couldn't find a map for the Russian flu. The other maps I found focused on the geographic spread of the disease, rather than the number of cases per country. /9
Here's the 1968 H3N2 / Hong Kong flu. It actually looks similar to coronavirus in the timing of its spread: originated in Asia, spread to Europe & North America within two months, largely avoided Africa & Asia. Source: edrybicki.wordpress.com/virology-ebook… /10
Here's the 1957 H2N2 Asian flu. This one did hit African countries. I couldn't find good data on the number of cases in Africa; please share if anyone has it. Map source: ocw.jhsph.edu/index.cfm/go/i… /11
Finally, here's the H1N1 Spanish flu (1918). The first wave of infections hit the continent hard. Map source: thinglink.com/scene/78478192… /12
Over 2 million African soldiers served in colonial armies during WWI (qz.com/africa/1316060…). Returning soldiers brought the flu home. Nearly 2% of *the entire African population* died of the Spanish flu, one of the highest mortality rates anywhere (encyclopedia.1914-1918-online.net/article/influe…) /13
Just to repeat, we can't necessarily predict anything about coronavirus from these maps. Some past pandemics have largely bypassed African countries and others have seriously affected them. Different diseases, health systems, etc. /end
