In June 2016, a WHO representative in Luanda said that the initial investigation of the outbreak in December was thrown off course because the first cases in December 2015—the sick Eritrean visitors—had what were later identified as fake yellow fever vaccination certificates. All had been to the same restaurant, so food poisoning was initially suspected as the cause of the mystery illness. It was more than a month before blood samples from the Eritreans reached the Pasteur Institute lab and yellow fever was recognized. Public health experts identified that as one factor that delayed the response to the outbreak, which came close to being a much larger disaster, if vaccine supplies had not been successfully raised in time, or the disease had spread to other countries and continents. The concurrent Zika outbreak drew attention away from a potentially far more serious epidemic of yellow fever.