Ohio and Indiana each have reported their first cases of the Zika virus, bringing the total number of states with patients suffering from the disease to 13, in addition to Washington, D.C. Neither of the two cases announced Tuesday were from domestic spread of the disease; no such cases have been reported in the U.S. Both new patients recently traveled to Haiti. The Zika outbreak has spread in South and Central America, Mexico and the Caribbean.

Prior to Tuesday, there were at least 35 reported cases of travel-associated Zika virus in addition to nine cases that were locally acquired outside of the country but in U.S. territories, according to the Centers for Disease Control and Prevention. The other states that have reported a Zika case are Arkansas, California, Florida, Georgia, Hawaii, Illinois, Massachusetts, Minnesota, New Jersey, Texas and Virginia. Puerto Rico had nine cases, including one locally acquired. The U.S. Virgin Islands had one case, which was also locally acquired.

The Zika virus outbreak and international media attention have resulted in especially strong concern that this summer’s Olympic Games in Rio de Janiero could contribute to further spread of the disease. Kenya is considering skipping the Games to avoid bringing the virus back home.

The main concern with the Zika virus, which is transmitted through mosquito bites, has been in relation to its effect on pregnant women. Children born to mothers with the virus have an increased risk of severe cranial deformity that can be fatal in some cases. That risk has resulted in an urgent debate in Latin American countries that have very restrictive laws on abortion. Already in Brazil, where the virus been particularly devastating for lower-income and impoverished communities, health officials have advised women to avoid becoming pregnant.

Symptoms of the virus include fever, rashes, joint pain and red eyes. It does not frequently result in hospital visits.