Brazil has more than 4,000 suspected and 400 confirmed cases of microcephaly among newborn babies, the country's health minister says, with many strongly suspected of being caused by the Zika virus.
The announcement came as health ministers from Mercosur-member countries gathered on Wednesday in the Uruguay capital of Montevideo for the first regional conference on the Zika outbreak.
Marcelo Castro confirmed that experts from the US would arrive in Brazil "to carry out a high-level meeting during which we will determine the first steps and the agenda for developing this vaccine".
"Brazil is taking effective measures on various fronts," he said.
"One of them, which is the most important in terms of the future, is an agreement with various and diverse laboratories for the development of a vaccine."
READ MORE: The Stream - Understanding the Zika threat
Despite the high number of suspected microcephaly cases among Brazil's newborn babies, however, a large number are expected to be "false positive" results.
Al Jazeera's Teresa Bo, reporting from Montevideo, said dealing with the Zika virus was not just a health issue for the affected countries but also a political, social and economic one.
"Governments are advising their citizens not to travel to affected areas," she said.
"For example, Brazil is a holiday destination. Over two million Argentines are on holiday this year to Brazil alone. It is also hosting the Olympics. So stopping people from travelling there is going to have an economic effect.
"Also, the Zika outbreak has opened the debate about abortion in Latin America where it remains illegal in many countries."
The World Health Organization declared a global health emergency on Monday, meaning that its 194 member states must now work together to investigate the cause of the problem.
This is the fourth global health emergency declared by the WHO since the system was established in 2005, and is a way for the UN health body to force its members to act in the interests of global public health.
The virus, which may be connected to thousands of birth defects in the Americas, is primarily spread through mosquito bites, but investigators are exploring the possibility it could be sexually transmitted.
On Tuesday a person in Texas was declared infected with the Zika virus, possibly through sexual intercourse, in the first case of the illness being transmitted in the US.
The unidentified person had not travelled abroad but had sex with a person who returned from Venezuela and contracted Zika, Dallas county health officials said on Tuesday.
READ MORE: Zika virus facts you need to know
The US Center for Disease Control (CDC) issued a statement saying lab tests confirmed the non-traveller was infected with Zika.
A Colorado researcher who picked up the virus in Africa reportedly infected his wife back home in 2008, and Zika was found in one man's semen in Tahiti.
"It's very rare but this is not new," Zachary Thompson, director of the Dallas County Health and Human Services, told WFAA-TV in Dallas.
"We always looked at the point that this could be transmitted sexually."
The CDC said it would issue guidance in the coming days on prevention of sexual transmission of the Zika virus, focusing on the male sexual partners of women who are or may be pregnant.
Source: Al Jazeera and agencies