Zika virus Outbreak - Expert reaction

Zika virus outbreak - Expert reaction

Concern over the current outbreak of the mosquito-spread Zika virus in the Americas is growing.

The virus is likely to spread to all countries in the Americas except for Canada and Chile, the World Health Organization said yesterday. The US Centres for Disease Control currently lists 22 countries with active transmission of the virus, including Samoa.

The virus, initially thought only to cause mild fever and rashes, has now been tentatively linked to increases in the incidence of microcephaly - incomplete brain development - in newborns.

The New Zealand Ministry of Health has updated its information and advice on the Zika virus on the Ministry website.

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Dr José G B Derraik, Senior Research Fellow, Liggins Institute, University of Auckland, comments:

"There are a number of possible reasons for the major outbreak of Zika virus in Latin America. One important factor is that the populations in this region had never been exposed to Zika virus and therefore have no immunity to it, so that it was able to spread rather quickly. However, it is also possible, for example, that the virus has mutated since its discovery in Uganda in 1947, becoming more infectious.

"The causative association between Zika and microcephaly has not been conclusively proven. However, the virus has been detected in the amniotic fluid from pregnancies with microcephaly, and the latest evidence from Brazil indicates that the virus can indeed cross the placenta and infect the developing fetus. The reports from Brazil indicate that Zika virus infection in pregnant women can lead to microcephaly in the unborn child as well as other adverse pregnancy outcomes, such as miscarriage.

"There have been outbreaks of Zika virus in the South Pacific already, including New Caledonia, Cook Islands, and Samoa. Travellers infected with exotic viruses (including Zika) arrive in New Zealand regularly. However, the risk of an outbreak ofZika virus in New Zealand is low compared to many nations, as the main mosquito vector of the virus Aedes aegypti and other efficient vectors such as Aedes albopictus are not present in the country.

"However, we do not know whether the mosquitoes present in New Zealand can transmit Zika virus."

Dr Siouxsie Wiles, Senior Lecturer, Faculty of Medical and Health Sciences, University of Auckland, put together a FAQ on Zika for Sciblogs.co.nz. She writes: What are the symptoms of Zika infection?

"Until recently, the Zika virus was thought to give people a mild infection. About 2-7 days after a mosquito bite, 1 in 4 people develop symptoms which could include a mild fever, conjunctivitis, a headache, joint pain and a rash. But since October 2015, there have been over 3,500 babies born in Brazil with microcephaly – a quite uncommon complication of pregnancy in which babies brains don’t develop properly and they are born with a smaller head and brain. "The WHO is also investigating an increase of Guillain-Barré Syndrome (GBS) cases in El Salvador. GBS is an autoimmune disease caused by the body’s immune system mistakenly attacking the peripheral nerve. "There is currently no treatment or vaccine for Zika. The main way to avoid infection is to prevent being bitten by mosquitoes and to try to stop Aedes mosquitoes breeding. Women in outbreak countries are currently being advised to delay getting pregnant. What’s the risk to NZ?

"According to the Ministry of Health website, we don’t have the right mosquitoes in New Zealand for the Zika virus to flourish here. The main risk to New Zealanders is travelling to countries with widespread Zika transmission. This list of countries seems to be growing by the day, but most relevant to New Zealanders is probably Samoa.

"The CDC is advising women who are pregnant, or trying to get pregnant, to postpone travelling to countries with Zika, and if this can’t be done, to take all precautions to avoid being bitten by mosquitoes. This means using mosquito nets, covering up arms and legs with long clothing, and using proper insect repellents that contain DEET or picaridin. Now is not the time to be relying on ‘chemical-free’/homeopathic repellents or nonsense vitamin B patches."

Read the full FAQ on Sciblogs.co.nz Earlier commentary collected over the weekend by the UK SMC (read the full comments on the Science Media Centre website).

Prof Laura Rodrigues, Professor of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, said:

"This is a very new situation. Until a few months ago we did not know that Zika could cause congenital infections and microcephaly. It caught us all by surprise. There was very little research as Zika was seen as a virus of no public health importance. There is no vaccine, we do not know if a case becomes immune, there is no good diagnostic test and no treatment. Much research needs to be done - will be done - with a major international effort we hope to have better knowledge and maybe a vaccine in a couple of years." Prof Andrew Easton, Professor of Virology, University of Warwick, said:

"The virus was introduced into South America in probably in late 2014. This was most likely due to an infected person (who may have had no symptoms of disease) being bitten by a mosquito which then transferred the virus to other people. Mosquitoes are a major concern in that part of the world as they transmit a number of other diseases and they are extremely numerous.

"In parts of the world where mosquitoes do not survive well or are relatively uncommon transmission of the virus by a returning infected traveller is unlikely to represent a problem.

"It has only been in the last few months that there have been suggestions of Zikavirus infection leading to problems with newborns. In French Polynesia there was a significant increase in the incidence of microcephaly and, as we have seen recently in Brazil, this appears also to be the case there with up to 4000 cases in a very short period. Some studies have detected Zika virus in the fluid that surrounds the embryo during pregnancy and this suggests that infection of foetus in the womb can lead to these problems, though this is still an area of active investigation. These investigations will become more urgent in light of the huge increase in incidence of complications.

"The link between Zika virus infection of pregnant women and microcephaly has not yet been definitively proven but the increase in spread of the virus incidence alongside the increase in microcephaly is a concern." Prof Trudie Lang, Director of the Global Health Network, University of Oxford, said:

"This virus is not like Ebola in that there is no evidence for human to human transmission; Zika is not contagious.

"However, this is an important emerging disease outbreak situation and we really must apply the lessons that we learnt from Ebola because Zika could be a major public health issue in these countries. There are many unknowns and so research is urgently needed to understand what is happening and how to prevent further cases.

"There is no treatment and no vaccine and so this would need addressing through clinical trials as quickly as possible. The international research community are pulling together through the ISARIC network to support local health research groups to set up studies as quickly as possible by sharing research methods and protocols.

"During the Ebola outbreak the research response was too slow and lagged behind the immediate medical humanitarian action. Research simply must be embedded in the global response to emerging outbreaks such as this in order that the impact to public health is limited by understanding the disease and evaluating interventions such as prevention strategies, treatments and vaccines."

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