By breaking contagion down into its basic DOTS components –
duration, opportunities, transmission probability, susceptibility – and
thinking about how network structure affects contagion, we can also
estimate the risk posed by a new STI. In 2008, an American scientist
returned home to Colorado after a month working in Senegal. A week
later, he’d fallen ill with a headache, extreme tiredness, and a rash on
his torso. Soon after, his wife – who hadn’t travelled – developed the
same symptoms. Subsequent lab tests indicated both had been
exposed to the Zika virus. Prior Zika research had focused on
transmission from mosquitoes, but the Colorado incident suggested
the virus had access to another route: it could infect people during
sexual encounters.[62] As Zika spread around the globe in 2015–16,
more reports of sexual transmission would follow, fueling speculation
about a new type of outbreak. ‘Zika: The Millennials’ S.T.D.?’ asked
one opinion piece in the New York Times during 2016.[63]
Based on the DOTS for Zika, our research group estimated that
the reproduction number for sexual transmission was below one; the
virus would probably not cause an STI epidemic. Zika could
potentially cause small outbreaks in groups with a lot of sexual
contacts, but it was unlikely to pose a major risk in areas without
mosquitoes.[64] Unfortunately, the same has not been true for other
STIs.
G , charming, and had a lot of sex. A
Canadian flight attendant, he’d slept with over two hundred men a
year prior to March 1984, when he died of a few weeks after his
31st birthday. Three years later, journalist Randy Shilts featured
Dugas in his bestselling book And the Band Played On. Shilts
suggested that Dugas had played a central part in the early spread of
the disease. He dubbed Dugas ‘patient zero’, a term still used today
to refer to the first case in an outbreak. Shilts’ book fuelled
speculation that Dugas was the person who introduced the epidemic
to North America. The New York Post called him ‘The Man Who Gave
Us ’; the National Review said he was ‘the Columbus of ’.
The idea of Dugas as patient zero was certainly attention-grabbing,
and has been repeated often in the decades since. But it turned out