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Zika symptoms more severe than expected in small Canadian cohort
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More people than expected suffered severe Zika virus symptoms among a small group of Canadian travelers who contracted the disease abroad, according to a study.
Two patients had symptoms of Guillain-Barré syndrome, which have previously been associated with Zika cases, and two pregnancies resulted in congenital transmission among the 41 patients with the virus.
“The common perception that Zika is associated with a very mild clinical course compared with dengue or chikungunya was not borne out in this small cohort,” study researcher Andrea K. Boggild, MD, clinical director of the tropical disease unit at the University Health Network, University of Toronto and Public Health Ontario, said in a news release.
The researchers suggested that relying only on data from areas where Zika is most prevalent and ignoring those that come from other affected areas may hide the true extent of complications caused by the virus.
They examined data on 1,118 travelers who visited any of seven clinics associated with the Canadian Travel Medicine Network — a group of specialists who treat travel-related sickness in the country. The patients arrived at the clinics throughout Canada between October 2015 and September 2016, after visiting countries in Central America, the Caribbean or South America.
The researchers found that dengue affected 41 patients (3.7%), whereas chikungunya affected 23 (2.1%).
Of the 41 who had Zika, 24 were women. Two of the three pregnant women among them passed the virus on congenitally. They and the two patients who had Guillain-Barré syndrome symptoms — one of whom also had Zika viral meningitis — were considered the severe cases. They accounted for nearly 10% of the patients with Zika. None of those infected with dengue experienced severe symptoms.
Regarding less severe symptoms, 36 patients (88%) reported a rash, 33 (80%) had a fever, 22 (54%) had arthralgia, 19 (46%) experienced myalgia, 17 (41%) had a headache and five (12%) had conjunctivitis.
Forty of the patients with Zika were likely infected by mosquitos, the researchers wrote. The virus was transmitted sexually in the remaining case, they added, from a partner who had visited the Caribbean.
The most common regions in which infections took place clearly changed over the course of the study. From October 2015 to March 2016, 54% of the Zika infections took place in South America. That proportion dropped to 4% from April to September (P = .001).
Likewise, from October to March, 46% of infections occurred in the Caribbean or Central America, as compared with 93% in those regions from April to September.
The researchers also emphasized the fact that, although dengue is one of the most common causes of fever among returning travelers, Zika was just as prominent in the study, “which highlights the emergence of this arboviral pathogen in the mobile Canadian population,” they wrote.
“Prevention of transmission rests on mosquito avoidance measures, which may include travel deferral, and on barrier protection during sexual activity.” – by Joe Green
Disclosure: Bogglid reports serving on the Committee to Advise on Tropical Medicine and Travel, an external advisory body to the public Health Agency of Canada. Please see the full study for a list of all other authors’ relevant financial disclosures.
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