Dr José G B Derraik

Senior Research Fellow, Liggins Institute University of Auckland

中南米でジカ熱が大流行している背景には、これまでこの地域にジカウイルスが入ってこなかったために、人々に免疫がないことがあります。ジカウイルスは1947年にウガンダで発見されましたが、現在のウイルスは変異しており、感染力が増しています。ジカウイルス感染と小頭症との関連は完全には明らかにされていませんが、ブラジルでにおける小頭症の急増は、ジカウイルスが胎盤を通過し、胎児にも感染できることを示唆しています。

原文

"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 of Zika 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

ジカウイルスはウイルスをもつ蚊に刺されることで感染します。感染後は4人に1人の割合で、約2〜7日後に軽度の発熱、結膜炎、頭痛、関節痛、発疹などがみられます。ブラジルでは、2015年10月以降、3500人以上の先天性小頭症の子どもが生まれています（翻訳者補足:先天性小頭症では運動機能や知能に障害がみられる。その程度には個人差がある）。WHOは、エルサルバドルにおけるギランバレー症候群の増加とジカウイルスの関連についても調べ始めています。ギランバレー症候群は、免疫系が誤って自身の末梢神経を攻撃する自己免疫疾患です。

現時点では、ジカ熱の治療薬やジカウイルスワクチンはありません。媒介する蚊（ネッタイシマカやヒトスジシマカ）に刺されないようにし、流行国に住む女性は、流行中は妊娠しないように気をつけることが望ましいといえます。蚊の繁殖を防ぐ対策も検討されるべきでしょう。他国の妊婦は流行国に行かないようにし、やむを得ない場合は、蚊に刺されないよう、考えうるすべての予防措置を取ってください。

原文

"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."