(CN) – New research shows the Zika virus can lead to a variety of health conditions in adults, a group previously believed to experience mostly minor symptoms after contracting the virus.
The findings come from one of three studies on the effects of the Zika outbreak in Brazil, which will be presented at the annual meeting of the Radiological Society of North America beginning Nov. 28.
Several adults examined in the study exhibited symptoms of Guillain-Barre syndrome, a rare disorder that causes rapid-onset muscle weakness and can result in paralysis. MRIs showed inflammation of the spinal cord and brain, and enhanced facial and spinal nerves in several patients.
Zika is generally believed cause only minor symptoms in adults, and many infections go unnoticed as a result. However, infections in adults have also been connected to more severe health issues in rare situations, including Guillain-Barre. The study suggests the risk Zika poses to adults could be broader and more serious than previously expected.
"It was alarming to find so many cases of neurological syndromes in adults, some very serious, related to Zika virus infection," said study author Emerson de Melo Casagrande, a doctor at Antonio Pedro University Hospital in Brazil.
Another study looked at CT scans of the central nervous systems of 16 newborn babies infected with congenital Zika virus. The showed decreased brain volume, calcification, prominent occipital bones and heart damage.
"We live in Pernambuco, a state in northeastern Brazil, which had the highest number of patients with microcephaly during the Zika outbreak in our country," said study author Natacha Calheiros de Lima Petribu, a doctor from Barao de Lucena Hospital in Brazil. "Our study proves that Zika virus infection can cause congenital brain damage in babies with and without microcephaly."
A third study performed ultrasound and fetal MRIs on pregnant patients with Zika infections at different stages of pregnancy. Once their babies were born, they underwent ultrasound, MRI and CT scans, which the researchers used to create 3-D physical and virtual models of their skulls.
More than half of the babies had microcephaly, a congenital disorder that results in reduced head size and potential brain damage. The infants also had brain calcification, structural changes and loss of brain tissue volume.
“An early diagnosis may help in treating these babies after birth,” said study author Heron Werner from Clinica de Diagnostico por Imagem in Brazil. “Moreover, the knowledge of abnormalities present in the central nervous system may give hints about the pathophysiology of the disease.”
Even babies born apparently healthy and normal after contracting Zika are developing symptoms of microcephaly-like symptoms several months after birth, according to a separate study published Tuesday by the U.S. Centers for Disease Control and Prevention.
The research was led by Vanessa Van der Linden, a pediatric neurologist in Recife, Brazil, who helped alert the international health community to Zika after Brazil experienced local active transmission of the virus and infected babies were diagnosed with microcephaly or other congenital neurological disorders.
Van der Linden’s team examined 13 babies who were infected with the mosquito-borne virus but were born apparently unaffected.
Despite appearing healthy, most of the babies eventually developed symptoms of disorders previously connected to Zika.
“Among all infants, head growth was documented to have decelerated as early as 5 months of age and 11 infants had microcephaly,” the authors write.
Ten of the children had trouble feeding, and seven had epilepsy – a common diagnosis of Zika-affected babies. Almost all of the infants had a stiffening of the limbs called hypertonia.
“These findings demonstrate the importance of early neuroimaging for infants exposed to Zika virus prenatally and the need for comprehensive medical and developmental follow-up,” the team found.
State and federal health officials declared Tuesday that two areas of Miami Beach are free of local Zika transmission, meaning that no one has acquired the virus there in the past 45 days.
Florida Gov. Rick Scott visited the barrier island east of Miami, one of three sections of South Florida designated as a Zika zone. The designation prompted the CDC to issue travel warnings to pregnant women due to Zika’s connection to birth defects.
“I am proud to announce that three miles of the impacted area in Miami Beach have been cleared of any ongoing active transmission of the Zika virus,” Scott said.
Florida is the only state where the virus has been spread locally by mosquitoes, leading to 236 confirmed infections confined mostly to three Miami neighborhoods.
“We understand this has been a difficult time for Miami Beach residents and tourists, and thank local and state officials for their hard work to interrupt the spread of the virus in the area,” CDC director Tom Frieden said.
After starting in Brazil in 2015, the current Zika epidemic spread to nations throughout Latin America and the Caribbean – with cases also discovered in parts of Europe and Asia.
Of the Zika cases reported in 49 U.S. states – Alaska is the only state without a diagnosed case – almost all of the infections were contracted while traveling to a foreign nation experiencing local active transmission of the virus.
The CDC advises that all pregnant women be evaluated for possible Zika exposure during each prenatal care visit.