Zika Reported in Rio de Janeiro, Site of 2016 Summer Olympics

In the first report of a Zika outbreak in the Brazilian state of Rio de Janeiro, researchers from the Acute Febrile Illnesses Laboratory at the Evandro Chagas National Institute of Infectious Diseases and the Oswaldo Cruz Foundation, revealed that the disease has been circulating in the region since at least January of 2015. The researchers also identified more than 300 suspected cases over a six-month period last year.

The findings are significant because, although healthcare personnel across the Latin American nation have been concerned about the mosquito-born virus since early last year, the epicenter of the outbreak has been concentrated to low-lying areas in the northeastern part of the country. The fact that Zika, which has been linked with microcephaly (incomplete brain development in newborns among infected pregnant women) and other complications, is now circulating within Brazil’s second largest city and biggest tourism center, as well as the site of the 2016 Summer Olympics, is, needless to say, a cause for some alarm.

As part of their surveillance protocol for monitoring three ongoing public health emergencies in Brazil—Zika, Chikungunya, and Dengue—the research team initially launched a syndromic clinical observational study in 2007 to capture unusual presentations of Dengue virus infections. Starting in January 2015, they noted an increase in the number of cases with exanthematic disease clinically distinct from Dengue. The researchers noted that more than half of these patients reported headache, arthralgia, myalgia, non-purulent conjunctivitis, and lower back pain, consistent with the Pan American Health Organization (PAHO) case definition of Zika. However, fever, when present, was low-intensity and short-termed.

According to their report, published online on April 12 by PLOS Neglected Tropic Diseases, physicians at the center evaluated these patients using the laboratory diagnostic algorithm for detection of Chikungunya, Dengue, and Zika and found 364 suspected cases of the latter between January and July of 2015 alone. Of these cases, 262 (71.9%) were tested and 119 (45.4%) were confirmed by the detection of Zika virus RNA.

Interestingly, the authors estimate that 11% of the confirmed cases in their study date back to the months before Zika virus transmission was first reported in the northeastern region of Brazil in May 2015, and they write that the virus was “possibly introduced to Rio de Janeiro during the VI World Sprint Championship canoe race in August 2014,” which included teams from French Polynesia, New Caledonia, Cook Islands, and Easter Island, where the virus had been circulating at the time.

Based on their findings, the authors of the PLOS paper recommend that pruritus, the second most common clinical sign presented by the confirmed Zika cases in their study, be added to the PAHO’s case definition for the disease.

Although they could not be reached for comment at press time, the authors noted in their concluding remarks that, “the emergence of Zika virus as a new pathogen for Brazil in 2015 underscores the ease with which pathogens travel between continents and the need for clinical vigilance and strong epidemiological and laboratory surveillance systems. In 2016, Rio de Janeiro will be hosting the Summer Olympics and Paralympics games, which will attract a high number of national and international visitors. Reliable and sensitive surveillance of arboviral disease that includes a system for the detection of emerging pathogens is of paramount importance to manage the complex challenges ahead.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.