Police said 2,500 people demonstrated outside the presidential palace in the capital of Brasilia.
Critics slammed Lula's return as a desperate attempt by President Dilma Rousseff to shore up support.
A new study conducted with cell cultures shows how the mosquito-borne virus may slow down and stop neural cell growth.
A group of Brazilian doctors suspected the connection between Zika and microcephaly months ago, but had to persuade their government, and the world, that they were onto something real.
A malicious spam campaign seeks to capitalize on fears surrounding the Zika virus.
Pope Francis added that he still considers abortion a crime.
The woman was diagnosed in Catalonia after returning from Colombia.
The donor had developed symptoms that originally were mistaken for dengue, a virus borne by the same mosquito that transmits Zika.
The World Health Organization has declared a global emergency but Olympics chiefs remain unruffled.
The WHO says it is taking immediate action to expedite research on the causal relationship between the outbreak of the virus and the growing rate of infant birth defects in Brazil.
Zika's risk to babies is now a public health emergency.
Health officials say they have not yet seen a case of local transmission in the U.S.
Brazil now joins India, Burkina Faso and Thailand at 76th place on the list.
The virus has been linked to birth defects in Brazil, including almost 4,000 suspected cases of microcephaly.
This is the second time prison inmates have escaped in the area in less than a week.
Brazilian police searched the home of Eduardo Cunha on Tuesday as part of a series of anti-graft raids against senior political figures.
But the real test of the popular mood will come when Brazil returns from its summer holidays to face a deepening recession and fewer jobs.
Former President Luiz Inacio Lula da Silva is not under investigation.
The ruling provided respite for Rousseff as she struggles to fend off the effort to unseat her.