to be fiction. In 2016, a team of researchers published an analysis of
viruses from a range of patients, including men diagnosed with
in the 1970s and Dugas himself. Based on the genetic diversity
of these viruses and the rate of evolution, the team estimated that
had arrived into North America in 1970 or 1971. However, they
found no evidence that Dugas had introduced to the US. He was
just another case in a much wider epidemic.[65]
So how did the patient zero designation come about? In the
original outbreak investigation, Dugas hadn’t actually been listed as
‘Patient 0’, but rather as ‘Patient O’, the ‘O’ short for ‘Outside
California’. In 1984, William Darrow, a researcher with the Centers for
Disease Control and Prevention (CDC), had been assigned to
investigate a cluster of deaths among gay men in Los Angeles.[66]
The CDC generally gave each case a number based on the order in
which they had been reported, but the cases had been relabelled for
the LA analysis. Before Dugas had been linked to the Los Angeles
cluster, he was simply ‘Patient 057’.
When investigators traced how the cases were linked, it suggested
that the deaths might be the result of an as-yet-unknown STI. Dugas
appeared prominently in the network, with links to multiple cases in
New York and LA. This was in part because he’d tried to help the
investigators, naming 72 of his partners in the preceding three years.
Darrow pointed out that this had always been the aim of the
investigation: to understand how cases were linked, rather than find
out who had started the outbreak. ‘I never said that he was the first
case in the United States,’ he later commented.
When investigating outbreaks, we face a gap between what we
want to know and what we can measure. Ideally, we’d have data on
all the ways in which people are connected, and how infection has
spread through these links. What we can actually measure is very
different. A typical outbreak investigation will reconstruct some of the
links between people who were infected. Depending on which cases
and links are reported, the resulting network won’t necessarily look
like the actual transmission route. Some people might appear more
prominent than they really were, while some transmission events
might be missed.