Research links Zika virus with disorder which can paralyse and kill
Zika virus may cause a rare but terrifying neurological disorder that can paralyse and kill, scientists believe.
New research from a Zika hotspot has linked the mosquito-borne infection with Guillain-Barre syndrome (GBS), which affects the immune and nervous systems.
Scientists made the discovery after analysing blood samples from 42 people diagnosed with GBS during a major Zika outbreak in French Polynesia between October 2013 and April 2014.
Of the patients, 88% had reported symptoms of Zika infection six days before they began to experience neurological problems.
Zika has already been found to affect unborn babies, causing them to be born with abnormally small heads and brain damage.
Recently, it has also been linked to another foetal disorder marked by tissues swelling with fluid, and stillbirth.
Professor Arnaud Fontanet, from the Pasteur Institute in Paris, led the latest research published in The Lancet medical journal.
He said: "This is the first study to look at a large number of patients who developed Guillain-Barre syndrome following Zika virus infection and provide evidence that Zika virus can cause GBS.
"Most of the patients with GBS reported they had experienced symptoms of Zika virus infection on average six days before any neurological symptoms, and all carried Zika virus antibodies."
The data from French Polynesia suggests that if 100,000 people were infected with the virus, 24 would be expected to develop the disorder, which is associated with bacterial or viral infections.
In Europe and North America, GBS affects only about one or two people in every 100,000 each year.
Prof Fontanet added: "Although it is unknown whether attack rates of Zika virus epidemics will be as high in affected regions in Latin America than in the Pacific Islands, high numbers of cases of Guillain-Barre syndrome might be expected in the coming months as the result of this association.
"The results of our study support that Zika virus should be added to the list of infectious pathogens susceptible to cause Guillain-Barre syndrome."
Symptoms of GBS develop rapidly over a period of two to four weeks and include weakness in the legs and arms and muscle pain.
In about 20% - 30% of cases, severe GBS can lead to respiratory failure, and about 5% of patients die. The disease can cause paralysis of muscles affecting speech, swallowing, and breathing.
The study ruled out the possibility that past infection with dengue, another tropical viral disease spread by mosquitoes, increased the risk of GBS among the Zika-infected patients.
All 42 patients were diagnosed with a type of GBS called acute-motor axonal neuropathy (AMAN). But few carried biological markers associated with AMAN, suggesting a previously unknown disease mechanism.
Of the patients, 16 were given intensive care in hospital and 12 required breathing assistance. Three months after being discharged from hospital, 57% of the patients were able to walk unaided and none died.
Symptoms of GBS usually appear after a mild infection of the sort that causes cold symptoms, a sore throat or stomach upset.
The disease is thought to be triggered by the immune system running out of control and attacking the body's own peripheral nerves.
Dr Jeremy Farrar, director of the Wellcome Trust, which co-funded the research, said: "This study provides the most compelling evidence to date of a causative link between Zika virus infection and the serious neurological condition Guillain-Barre syndrome.
"The scale of the crisis unfolding in Latin America has taken us all by surprise, and we should be prepared for further unforeseen complications of Zika virus infection to emerge in the coming weeks and months.
"What's important now is that the global community comes together to focus research efforts on the many unanswered questions about the virus, and to share this information rapidly so that the knowledge gained can benefit patients as quickly as possible."
Jimmy Whitworth, Professor of International Public Health, at the London School of Hygiene & Tropical Medicine, said: "If the experience of Zika virus infection in Latin America is similar to that seen in French Polynesia, we can expect to see about two to five cases of Guillain-Barre syndrome for every 10,000 people who get infected.
"This has implications for health care in countries with a Zika virus epidemic as a proportion of those affected with Guillain-Barre syndrome will need breathing support on a ventilator for a while, and some cases do not recover fully from the syndrome and are left with disability."