By March 2015 the virus appears in two more Brazilian states, then reaches Salvador, a city of 2.5 million. Doctors speculate that the symptoms are the result of an allergy; that it was roseola, a childhood illness; that it was a new variant of Fifth Disease, a facial rash that gives children a “slapped-cheek” look. Dr Soares, a biologist:
People were claiming it was polluted water. I began thinking it was something transmitted by mosquitoes.
Working in his modest lab with a colleague, Dr. Soares tests thousands blood samples. Other doctors are doing the same. Over 6,800 samples are tested from victims ranging from 4 months to 98 years old. Parvovirus, dengue, chikungunya and other suspects are all ruled out, leaving Zika as the cause in April. Dr Soares:
I actually felt a sense of relief. The literature said it was much less aggressive than viruses we already deal with in Brazil.