Zika Virus Update


Zika virus may be tied to acute disseminated encephalomyelitis



The Zika virus may be associated with an autoimmune disorder that attacks the brain’s myelin similar to multiple sclerosis, according to a small study that was presented at the American Academy of Neurology’s 68th Annual Meeting in Vancouver, in April.

“Though our study is small, it may provide evidence that in this case the virus has different effects on the brain than those identified in current studies,” said study author Maria Lucia Brito Ferreira, MD, with Restoration Hospital in Recife, Brazil. “Much more research will need to be done to explore whether there is a causal link between Zika and these brain problems.”

For the study, researchers followed people who came to the hospital in Recife from December 2014 to June 2015 with symptoms compatible with arboviruses, the family of viruses that includes Zika, dengue and chikungunya. Six people then developed neurologic symptoms that were consistent with autoimmune disorders and underwent exams and blood tests. The authors saw 151 cases with neurological manifestations during a period of December 2014 to December 2015.

All of the people came to the hospital with fever followed by a rash. Some also had severe itching, muscle and joint pain and red eyes. The neurologic symptoms started right away for some people and up to 15 days later for others.

Of the six people who had neurologic problems, two of the people developed acute disseminated encephalomyelitis (ADEM), a brief but severe attack of swelling of the brain and spinal cord. ADEM also attacks the nerves of the central nervous system and damages their myelin insulation, which, as a result, destroys the white matter. In both cases, brain scans showed signs of damage to the brain’s white matter. Unlike multiple sclerosis (MS), ADEM usually consists of a single attack that most people recover from within six months. In some cases, the disease can reoccur. Four of the people developed Guillain-Barré syndrome (GBS), a syndrome that damages the myelin of the peripheral nervous system and can lead to muscle weakness. It has a previously reported association with the Zika virus.

When they were discharged from the hospital, five of the six people still had problems with motor functioning. One person had vision problems and one had problems with memory and thinking skills.

Tests showed that the participants all had Zika virus. Tests for dengue and chikungunya were negative.

“This doesn’t mean that all people infected with Zika will experience these brain problems. Of those who have nervous system problems, most do not have brain symptoms,” said Ferreira. “However, our study may shed light on possible lingering effects the virus may be associated with in the brain.”

“At present, it does not seem that ADEM cases are occurring at a similarly high incidence as the GBS cases, but these findings from Brazil suggest that clinicians should be vigilant for the possible occurrence of ADEM and otherimmune-mediated illnesses of the central nervous system,” said James Sejvar, MD, with the Centers for Disease Control and Prevention in Atlanta and a member of the American Academy of Neurology. “Of course, the remaining question is ‘why’-why does Zika virus appear to have this strong association with GBS and potentially other immune/inflammatory diseases of the nervous system? Hopefully, ongoing investigations of Zika virus and immune-mediated neurologic disease will shed additional light on this important question.”

New research supports Zika virus-microcephaly link
New research, based on data from the 2013-14 Zika outbreak in French Polynesia, further supports the association between Zika virus and microcephaly. The study, published 15 March 2016 in The Lancet, estimates that the risk of microcephaly is about 1 for every 100 women infected with Zika virus during the first trimester of pregnancy.

The authors say that quantifying the risk may help better inform the broader public health response. Although the risk of microcephaly associated with Zika virus infection is relatively low compared to other maternal infections, the authors say that the association remains an important public health issue because the risk of Zika virus infection is particularly high during outbreaks, such as the current one in South America.

Commenting on the finding, Dr New research supports Zika virus-microcephaly link Laura Rodrigues, London School of Hygiene & Tropical Medicine, UK, said: “The finding that the highest risk of microcephaly was associated with infection in the first trimester of pregnancy is biologically plausible, given the timing of brain development and the type and severity of the neurological abnormalities.”

She noted that more research is needed. “Further data will soon be available from Pernambuco, Colombia, Rio de Janeiro, and maybe other sites…The fast production of knowledge during this epidemic is an opportunity to observe science in the making: from formulation of new
hypotheses and production of new results that will provide confirmations and contradictions to the refinement of methods and the gradual building of consensus.”

WHO EMR issues guide to keep region free of Zika
The World Health Organization (WHO) Regional Office for the Eastern Mediterranean invited representatives from ministries of health in the Region to two rounds of emergency meetings in February to share information on Zika virus infection and associated conditions and discuss implementation of public health measures to prepare for, and respond to, any possible spread in the Region. At the time of going to press, no case of Zika virus infection had been reported from any country in the Region, either through local transmission or importation via travel from a Zika-affected country. However, the Region remains at risk as the Aedes mosquito that transmits the virus to humans is present in at least eight countries – Djibouti, Egypt, Oman, Pakistan, Saudi Arabia, Somalia, Sudan and Yemen.

The meeting concluded with agreement on a set of recommendations for urgent implementation in order to keep the Region free from the threat of Zika virus infection. These included to:

  • enhance disease surveillance to early detect cases of Zika virus infection and notify WHO as soon as such cases occur;
  • establish laboratory facilities for diagnosis and testing capacities for Zika virus infection, including establishing appropriate links with external reference laboratories for sample processing;
  • strengthen entomological surveillance, especially in hotspot areas, including at ports and airports, to preempt and detect occurrence of high densities of Aedes mosquitoes and target these areas for vector control;
  • establish appropriate measures at points of entry, such as disinfecting conveyances arriving from a country with active Zika virus transmission;
  • conduct regular public awareness campaigns to proactively inform the public of the Zika virus situation focusing on travellers to areas with active transmission through issuance of appropriate advisories to reduce the possibility of exposure to mosquito bites;
  • urge communities to keep areas in and around the home free from mosquito breeding sites through applying appropriate risk communication messages and strategies in accordance with local culture and behavioural practice, and provide communities with the appropriate knowledge, information and tools to protect themselves from mosquito bites;
  • identify and establish a network of experts, reference laboratories and training centres in the region to support Member States in the areas of entomological surveillance, vector control, field investigation and laboratory detection;

WHO will implement this plan over the next several months in the Region, in collaboration with ministries of health and other regional and international health partners.

Sexual transmission
In March French researchers reported on a Zika virus link to meningoencephalitis and Italian researchers reported the first discovery of the virus in human saliva. These are just two examples from a wide range of new research on Zika and its potential sites of infection and routes of transmission.

The WHO says new studies on Zika and its complications are being published daily and the pace of research will continue to increase. The organisation says it will – with its partners – evaluate new studies to track any changes in the direction of the evidence base and to identify knowledge or research gaps.

The WHO says that “to allow publication of the latest evidence at regular intervals, a living systematic review is being developed. This will be an online summary of health research, which will be updated as new research becomes available.”

What is worrying about Zika is how much we don’t know. The US Centers for Disease Control and Prevention (CDC) issued a statement outlining the gaps in our knowledge of transmission of Zika.

What we know

  • Zika virus can be spread during sex by a man infected with Zika to his partners.
  • In known cases of sexual transmission, the men had Zika symptoms. From these cases, we know the virus can be spread when the man has symptoms, before symptoms start, and after symptoms end.
  • The virus can stay in semen longer than in blood.

What we do not know

  • We do not know how long the virus can stay in the semen of men who have had Zika.
  • We do not know if men infected with Zika who never develop symptoms can have the virus in their semen or spread Zika through sex.
  • We do not know if a woman can spread Zika to her sex partners. We do not know if Zika can be spread through oral sex, including vaginal fluids and saliva.

Date of upload: 15th May 2016

 

                                  
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