By Sabrina Tavernise

New York Times News Service

Zika babies — The images tell a heartbreaking story: Zika’s calamitous attack on the brains of babies — as seen from the inside.

A study of brain scans and ultrasound pictures of 45 Brazilian babies whose mothers were infected with Zika in pregnancy shows that the virus can inflict serious damage to many different parts of the fetal brain beyond microcephaly, the condition of unusually small heads that has become the sinister signature of Zika.

The images, published Tuesday in the journal Radiology, also suggest a grim possibility: Because some of the damage was seen in brain areas that continue to develop after birth, it may be that babies born without obvious impairment will experience problems as they grow.

Most of the babies in the study were born with microcephaly, although three were not. Each also suffered other impairments, almost all of which emerge earlier than microcephaly because a smaller head is really a consequence of a brain that has failed to develop fully or has been damaged along the way, experts said.

“The brain that should be there is not there,” said Dr. Deborah Levine, an author of the study and a professor of radiology at Harvard Medical School.

— The New York Times

When Florida announced a new case of the Zika virus on Tuesday, this time in Pinellas County, which includes St. Petersburg, it raised an urgent question: Had local mosquitoes in yet another part of the state started to spread the virus?

The short answer is probably not, scientists say. The announcement of the case in Pinellas, which is on the other side of the state from the current danger zone in Miami-Dade County, may sound scary, but the reality is that single cases are usually one-offs and do not necessarily mean that the virus is starting to spread in a new area.

For every nine or 10 individual cases of dengue and chikungunya, two mosquito-borne viruses that closely resemble Zika and have popped up in Florida in recent years, there is just one cluster, health officials said.

That means that there will likely be dozens of cases in the coming months that do not amount to much — just one person bit by one mosquito and nothing more.

“The vast majority of the local transmissions hit a dead end after one or two people in one household,” Dr. Thomas Frieden, the head of the Centers for Disease Control and Prevention, said in a briefing last week.

While the Pinellas case could still turn into a cluster, state officials took pains to say they do not have evidence of that yet. The Florida Department of Health “still believes ongoing active transmission is only taking place within the small identified areas in Wynwood and Miami Beach in Miami-Dade County,” Gov. Rick Scott said in a statement.

Health officials have been warning for months that Zika, which can cause severe brain damage in babies born to women who contract it during pregnancy, would arrive in the continental United States. Despite the number of homegrown cases in Florida — 42 as of Tuesday — officials do not believe that the virus will spread explosively in the United States like it has in Latin America and the Caribbean.

That is because the mosquitoes that carry it, the Aedes aegypti, are slow, and do not fly very far or live very long.

In Brazil, where the virus has raged since last year, one infected bug can do a lot of damage because people live in close quarters. But in the United States, where people are more spread out and often sealed up in air-conditioned houses or cars, even if an infected mosquito manages to bite someone, it is unlikely that the insect will live long enough or fly far enough to bite another.

“This is pretty much what we expected,” said Scott Weaver, the director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch. “The growth in cases is not exponential. It’s not as bad as some of the alarmist scenarios we’ve seen over the past few months.”