First report of Zika virus infection in a returned traveller from the Solomon Islands

A 33-year-old man returning from the Solomon Islands presented to an emergency department in Brisbane after 4 days of retro-orbital headache, fever, and myalgias, which had started 10 days into his journey. On examination, he was afebrile and had a diffuse erythematous rash. A full blood count revealed mild neutropenia and thrombocytopenia. IgG seroconversion for flavivirus was shown by parallel testing, 15 days apart. Zika virus (ZIKV) RNA was also found in blood, urine and throat samples by polymerase chain reaction (PCR) testing. The patient received supportive medical care and recovered fully.

ZIKV is a mosquito-borne flavivirus, first identified in the Zika forest of Uganda during yellow fever research in 1947; the first evidence for infection in humans was reported in 1952. Serosurveys during the 1950s suggested widespread ZIKV transmission in Africa and South-East Asia.1

ZIKV infection occurs in a geographical distribution, and causes a clinical syndrome similar to mild infection with dengue virus (DENV), also a flavivirus. Infection is characterised by fever, arthralgia, myalgia, headache and rash. Other features include peripheral oedema and non-purulent conjunctivitis. Symptoms abate within 3–12 days. Asymptomatic infection is common. ZIKV infection is not typically associated with blood film abnormalities, in contrast to infection with DENV or Chikungunya virus.2 There is neither a specific treatment for nor a vaccine against ZIKV infection. Management is supportive, and prevention consists of avoiding the primary vector, Aedes spp. mosquitoes, particularly A. aegypti.

Before 2007, only a handful of cases of ZIKV disease in humans had been reported. Since then, two large outbreaks in the Pacific Islands have occurred: the first in Micronesia in 2007, the second in French Polynesia in 2013. In each outbreak, most individuals had only mild symptoms.3

Reports of two imported cases of ZIKV infection in Australia have been published, including in a traveller returning to north Queensland,4,5 but this article is the first report in the scientific literature of ZIKV infection acquired in the Solomon Islands. Given the presence of A. aegypti in this region of Australia, a returning traveller with ZIKV viraemia could infect local mosquitoes, causing a local outbreak.

ZIKV is an emerging infectious disease in the Pacific Islands and beyond. It is now widely reported in Central and South America.6 Concerns about a possible association between ZIKV infection and poor neonatal outcomes resulting from infection during pregnancy, including microcephaly, have led to a surge in international interest in ZIKV.7 Cases will continue to be imported into Australia, including by returning travellers from the Solomon Islands. Clinicians should request ZIKV serology and PCR in travellers returning from the Pacific Islands with a DENV-like illness and negative serological tests for DENV, or with an isolated positive result for DENV IgM. Research is urgently required to understand the dynamics of ZIKV transmission and the association of ZIKV infection with adverse pregnancy outcomes in our own region.