The Zika virus—a mosquito-borne virus that usually causes mild flu-like symptoms—may be associated with more neurologic complications than originally thought. Microcephaly—a condition in which children are born with smaller-than-normal heads and varying degrees of brain damage—has been linked to the virus in several countries, according to the World Health Organization (WHO). The connection between Zika and microcephaly was recently confirmed by the US Centers for Disease Control and Prevention (CDC). Now, researchers are homing in on another condition possibly connected to Zika: Guillain-Barre syndrome (GBS).
The Syndrome
GBS, a neurologic disorder in which the immune system attacks part of the nervous system, causing temporary paralysis, is rare. In the United States, only about 1 case per 100,000 people is reported each year, according to the National Institute of Neurological Disorders and Stroke (NINDS). Researchers believe the syndrome may be triggered by an infection. In very rare cases, it has been linked to some vaccines, says Daniel Pastula, MD, a neurologist and medical epidemiologist at the University of Colorado Denver.
The Impact
About 5 percent of people who contract GBS die, and about 15 percent have significant lifelong muscle weakness or numbness and tingling in limbs, says Dr. Pastula. Treatment may include immunotherapy, such as intravenous immunoglobulin or plasma exchange, or mechanical ventilation if needed, he adds.
The Zika Link
The WHO has suspected a link between the Zika virus and GBS based on preliminary evidence that more than a dozen countries affected by Zika have also seen an increase in GBS cases. Results from a case-control study published in The Lancet in February strengthens the suspected link.
The investigators, led by Arnaud Fontanet, MD, DrPH, of the Emerging Diseases Epidemiology Unit at the Institut Pasteur in Paris, compared blood tests from three groups of patients at a local hospital in the capital of Tahiti during a Zika outbreak in 2013 and 2014: 42 patients with GBS, 70 patients who had been diagnosed with Zika but did not have GBS, and a control group of 98 who were in the same hospital but had no fever.
Study Results
The majority (98 percent) of patients with GBS reported symptoms of Zika—fever, rash, joint pain, or conjunctivitis—about six days before the symptoms of GBS appeared. The blood tests showed that all patients but one with GBS had antibodies against Zika while only 56 percent of patients in the control group had antibodies. Researchers thought a prior infection with dengue, another more common mosquito-borne virus, might have caused GBS, but they found that a past dengue infection did not increase the risk for Zika-associated GBS. Based on their study, the researchers estimate that during a Zika outbreak there could be 24 cases of GBS per 100,000 cases of Zika.
More Research Underway
Other researchers are exploring the link between GBS and the Zika virus. Public health authorities in Puerto Rico and Brazil, both of which are experiencing Zika outbreaks, are also trying to determine if there is an association between Zika and GBS. "I think it's likely that Zika virus infection is associated with GBS cases in these countries given The Lancet paper and anecdotal stories from Brazil and Central America," says Dr. Pastula. "Whether this is due solely to Zika virus infection, a confounder, or some combination of factors remains to be seen," he says. "More epidemiologic studies are currently underway."
Looking Ahead
Additional research may determine if something other than the Zika virus is linked to GBS or if GBS affects the body differently when triggered by the Zika virus—and the answers may affect treatment. "It is fair to say that Zika is the most likely cause of GBS-like syndrome [in Zika-affected countries], but it has not been shown that the GBS-like syndrome is due to an autoimmune phenomenon," says Avindra Nath, MD, FAAN, the clinical director of the NINDS, who served on the WHO panel on GBS. "If what is occurring in Zika-affected countries is not the same form of GBS previously known, it may need to be treated differently," he says.
Travel Precautions
The Zika virus has not been detected in the United States, but a small number of Americans who have traveled to affected regions have been diagnosed with the virus. "The incidence [of GBS in Zika-affected countries] is not so high that I would not travel," says Dr. Nath, "but you do want to take precautions to prevent mosquito bites. And pregnant women should certainly avoid travel to Zika-affected countries to reduce their risk of microcephaly."
The virus can also be spread during sex. A man infected by the virus can pass it to his partners, male or female, including to a woman who is already pregnant, according to the CDC. The CDC recommends that men who have been exposed to the Zika virus use a condom every time they have sex with a pregnant partner. This includes vaginal, anal, or oral sex.
Men and women who live in or have traveled to an area that's experiencing a Zika outbreak should talk to their health care providers before trying to get pregnant. The CDC recently updated its guidelines about planning a pregnancy after possible exposure to Zika, including suggested wait times for attempting to conceive.
