International tourism in 2015 grew by 50 million travelers putting the total number at 1.18 billion visitors who had traveled outside of their country. Those numbers may be threatened in 2016 by the Zika virus. As warnings increase for the mosquito-borne virus, the travel industry is beginning to feel the impact.

According to the World Health Organization (WHO), the Zika virus could infect as many as 4 million people in the Americas.

"The level of alarm is extremely high," says WHO Director-General Dr. Margaret Chan.

The virus has been linked to severe birth defects in babies and deaths of babies of mothers who were pregnant during travel, prompting warnings in locations where the virus has been found.

The Centers of Disease Control and Prevention has already issued a Level 2—Practice Enhanced Precautions travel warning for Puerto Rico, Mexico, Samoa, Cape Verde, as well as countries in Central America, South America and the Caribbean.

"Given the potential and increasingly strong association with these birth defects, this is a matter of some considerable concern," says Dr. Lyle Peterson, director of the Division of Vector-Borne Diseases.

As a result, many countries are creating guidelines for their tourism industries to help them prevent the spread of the virus and prepare for the virus.

The Caribbean Public Health Agency (CARPHA) and the Caribbean Hotel and Tourism Association (CHTA) have collaborated to create guideline for hoteliers in the area on how to deal with the situation.

The CARPHA warns hoteliers to stay informed about the Zika situation in their respective countries.

Hoteliers should also provide staff and guests with information on the Zika virus so that they are aware of the signs and symptoms, how the virus is transmitted and how it can be prevented.

In Brazil, the travel warning comes at the worst time as the country prepares for the Rio Olympics this summer. The alert was issued for the South American country after it was reported that microcephaly found in newborns were linked to the virus.

The Brazil Ministry of Health recently announced that test kits for quick detection of the Zika virus, chikungunya and dengue fever will be distributed to laboratories across the country beginning in February.

"We will distribute the tests that are required for this diagnosis to be made. There are plenty of resources in the Ministry of Health to combat microcephaly," said Brazilian Minister of Health Marcelo Castro.

The International Olympic Committee has predicted that approximately 500,000 tourists will travel to Rio for the Olympic and Paralympic Games.

"The Olympic and Paralympic venues will be inspected on a daily basis during the Rio 2016 Games to ensure that there are no puddles of stagnant water and therefore minimize the risk of coming into contact with mosquitoes," said Rio 2016 spokesman Philip Wilkinson.

"The Rio 2016 organizing committee is in regular contact with the Brazilian Ministry of Health and the Municipal Health department, which are the responsible authorities for guidance on health issues in Brazil and Rio. The organizing committee will follow the virus prevention and control measures provided by the authorities and provide relevant guidance to Games visitors."

With the increase of travelers cancelling their trips, the industry is dealing with how to handle those cancellations.

Cruise lines have begun waiving cancellation penalties for some customers who have booked cruises to the Caribbean and other regions affected by the Zika virus.

Carnival will allow pregnant women on trips that include stops in the U.S. Virgin Islands, Puerto Rico and other Zika-affected destinations to switch itineraries to unaffected areas.

"We are in close contact with public health officials regarding the recent Zika virus alert that provides specific guidance to pregnant women and those trying to become pregnant. We are proactively providing all guests with information regarding Zika. Pregnant women who wish to cancel their cruise will be provided alternate itinerary options that do not include destinations on the U.S. Centers for Disease Control’s list of Zika transmission areas. Alternately those guests may request a future cruise credit and re-schedule their voyage at a later date (at no penalty)," said Carnival in astatement.

Both Norwegian Cruise and Royal Caribbean are also providing similar options to their pregnant customers.

U.S. airlines are likewise offering similar options to their customers who are traveling to affected areas.

United and Delta are allowing customers to cancel or postpone their trips if they're ticketed to fly to affected areas. American Airlines will also allow pregnant women a similar option provided they have a note from their doctor.

As for hotels in the affected regions, they have yet to implement any cancellation policies because of the virus.

Hilton Worldwide says they are considering waivers for cancellation on a case by case basis. Ritz-Carlton hotels in Latin America and the Caribbean are educating employees on the virus and providing mosquito repellent for guests. Marriott says they are monitoring the ongoing situation with the Zika virus.

"Our hotels in the impacted areas are taking precautions; including fogging of outdoor areas, providing mosquito repellent for guest use, addressing areas of standing water, educating our employees on the virus and making information available to guests," said Marriott in a statement.

As Zika remains a fast-growing virus, the travel industry remains guarded and continues to monitor the situation as it continues to fold.