It has been almost a year since the outbreak of the Zika virus in Brazil in May 2015. Since then, the virus has spread throughout South America, becoming a “Public Health Emergency of International Concern” according to the World Health Organisation.
Additionally, it has been discovered that the virus is even more dangerous than first thought. The US Centers for Disease Control and Prevention (CDC) has confirmed the direct link between Zika and the rising number of cases of microcephaly in newborn babies. There is also evidence that the virus causes other birth defects, as well as rare autoimmune diseases in adults.
Zika is a vector-borne virus that is transmitted to humans by the female Aedes aegypti mosquito. Symptoms include mild fever, a rash, and conjunctivitis, which last for a few days. The effects of Zika on adults are usually minimal, with only one in five infected people showing any symptoms.
However, the virus can cause devastating abnormalities in developing foetuses. Since the current outbreak, there has been a dramatic rise in the number of babies born with microcephaly in Zika-affected countries, with 4,700 reported cases since October 2015 in Brazil alone. Microcephaly is a life-threatening congenital condition that causes babies to be born with unusually small heads and underdeveloped brains. Zika has been identified as the cause of the malformations, showing that the virus can be passed from infected mothers to foetuses transplacentally.
Even greater concerns about the virus were raised by Dr Anne Schuchat from the CDC during a recent White House press conference. It is now thought that Zika can cause a wider set of complications in foetuses, including prematurity and blindness. It was initially supposed that Zika was only dangerous to foetuses during the early gestation period, however, it is now thought that Zika can cause damage to foetuses during all stages of pregnancy.
Zika has also been linked to cases of autoimmune diseases in adults. The virus has been associated with Guillain-Barré syndrome, a disease that damages the peripheral nervous system, causing weakness and, in some cases, paralysis. Brazilian scientists have linked the virus with another autoimmune disorder, called acute disseminated encephalomyelitis (ADEM). The disease attacks the central nervous system, resulting in poor balance, visual impairments, and muscle weakness.
Worryingly, the geographical range of the Aedes aegypti mosquito has been underestimated. The mosquito is more prevalent in South America than previously thought, and is present in no fewer than 30 states. Amidst fears of the virus reaching North America, the CDC has urged states to prepare for “widespread local transmission in the continental US”.
There is currently no vaccine against the virus available, however experts from the National Institute of Health say that vaccine trials will begin this September, with further trials proposed for next year. There is a race to contain the outbreak ahead of preparations for the Olympic Games in Rio de Janeiro this coming August, when all eyes will be on Brazil.
Image: Muhammad Mahdi Karim