Ticket revenues for 2016 Rio Olympics events have dropped significantly since an outbreak of Zika virus in Brazil gained international attention.

From October until Jan. 20, 2016, ticket revenues for Olympics-related events were increasing an average of 8.85% each week, according to Ticketbis. In the second half of January, however, revenue dropped 56.4%, and continued to drop through at least the first half of February.

Optimistic analysts had predicted Olympics ticket revenues would return to normal — on a steady incline — by February.

"The public’s reaction to the travel alerts were directly reflected in the ticketing platforms revenue for the Olympic Games," a Ticketbis spokesperson said.

Searches for vacation rental listings on Tripping.com, however, show a slightly more optimistic picture. In the first week of February, searches for Brazil were up 49.8% compared to the week before, and up 12% from two weeks prior.

Brazilian officials have been optimistic about attendance at the summer games: The country has invested heavily in promoting tourism related to the Olympics, and throughout the summer.

Ironically, avoiding Brazil will not prevent many people from contracting Zika virus. The World Health Organization estimates 3 to 4 million people in the Americas will contract the virus.

The list of countries and territories with local Zika transmission — meaning mosquitoes in the region are spreading the virus — now includes Ecuador, El Salvador, Dominican Republic, Bolivia, Guatemala, Jamaica, Brazil, Costa Rica, American Samoa, Curaçao, Guadeloupe, Bonaire, Barbados, French Guiana, Mexico, Marshall Islands, Aruba, Cape Verde, Saint Vincent and the Grenadines, Trinidad and Tobago, Martinique, New Caledonia, U.S. Virgin Islands, Sint Maarten, Saint Martin, Tonga, Suriname, Samoa, Venezuela, Guyana, Haiti, Nicaragua, Panama, Honduras, Puerto Rico, Colombia and Paraguay.

The exception, announced Friday, is for elevations above 2,000 meters (6,500 feet). At and above that altitude, the CDC says, the risk of mosquito transmission is much lower.

However, as the CDC's illustration of Nicaragua — as just one example — shows, the elevation warning is not of much help to an overwhelming majority of people in the country.

Can you find the dots where risk of Zika transmission is lower? Image: Centers for Disease Control

While the illness associated with Zika is typically mild, and symptomatic in only about 20% of those who catch it, there is mounting evidence that the virus can cause more serious complications in some patients. The CDC has warned pregnant women to postpone travel to the countries listed above, as Zika could be causing increased cases of microcephaly, a condition which limits brain development in fetuses. Zika could also be causing Guillain-Barré syndrome, a condition in which the immune system attacks the nerves causing paralysis.

The Rio Olympics are scheduled for Aug. 5-21, 2016.

Correction: The story has been updated to reflect searches were for vacation rental listings on Tripping.com, not air travel.

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