Spread of Zika Virus Prompts Travel Advisories
Travel warnings about the Zika virus, especially for pregnant women, are very much in the news now, but the germ was discovered more than a half century ago, and you may have already visited places where it flourishes.
As of December 2015, the Centers for Disease Control and Prevention in Atlanta reported evidence of transmission of the virus in at least 45 countries in Africa, Asia, the Americas and the Pacific islands. There were cases reported in Mexico and El Salvador in November 2015, and one in Puerto Rico in December. Travelers should be concerned, but there is no need for panic.
截至2015年12月，亚特兰大的美国疾病控制与预防中心（Centers for Disease Control and Prevention，简称CDC）收集到了兹卡病毒在非洲、亚洲、美洲和太平洋岛屿上至少45个国家传播的证据。2015年11月，墨西哥和萨尔瓦多出现过这种病例，12月波多黎各也出现了一例。旅行者应该加以重视，但也没有必要恐慌。
“There are two things that make people pay attention,” said one expert, Dr. Kamran Khan, an infectious disease doctor and scientist at St. Michael’s Hospital in Toronto. “It showed up where it has never been before, and it is rapidly spreading. That’s because Aedes mosquitoes are widespread throughout most of Latin America and parts of the U.S.”
“有两件事情引起了人们的关注，”这方面的专家卡姆兰·汗博士(Kamran Khan)表示。“它出现在了以前没有到过的地方，而且还在迅速蔓延。这是因为伊蚊广泛分布在拉丁美洲大部分地区，以及美国的部分地区。”卡姆兰·汗是多伦多圣迈克尔医院(St. Michael’s Hospital)的传染病医生和科学家。
Mosquitoes of the Aedes species (the name derives from a Greek word for “unpleasant”) seem to be the main vector. These mosquitoes also spread dengue and chikungunya, two other, more severe, viral infections.
The virus was isolated in 1947 in the Zika Forest in Uganda. Researchers were studying the transmission of yellow fever, when they found the new virus in a rhesus monkey. Its first appearance in humans was in 1952 in Uganda and Tanzania, and the first large outbreak of disease was in 2007 on Yap Island in Micronesia.
There was an even larger outbreak in French Polynesia in October 2013, when about 10,000 cases were reported. In 2014, there were cases in New Caledonia and the Cook Islands in the South Pacific.
For most people, the Zika infection is not particularly serious. According to the C.D.C., only about 20 percent of infected people have any symptoms at all, and the few who become sick usually have a mild fever, sometimes diarrhea or a rash, headache or muscle pain. The illness goes away within a week, and rarely requires hospitalization. Rest, pain medication and hydration are the only treatments, and there is no cure or vaccine. There has never been a death attributed to the Zika virus, according to the C.D.C.
Still, there are significant dangers for pregnant women because the virus has been linked to congenital microcephaly, a serious and often fatal birth defect in which the fetal brain fails to develop properly.
The large outbreak in Brazil, which began in May 2015, is particularly worrisome because the number of cases of congenital microcephaly in newborns and stillborns has abruptly increased. It is possible that there is some other reason for this, but there is general agreement that until another association is found, the Zika virus should be assumed to be the cause.
No one knows how many people in Brazil are infected, but C.D.C. estimates range from 500,000 to 1.5 million. There have been about 3,500 cases of congenital microcephaly, according to Brazilian health authorities. On Jan. 15, the Hawaii State Health Department reported that a microcephalic baby infected with the virus had been born in Oahu, the first such case in the United States. The mother had lived in Brazil during part of her pregnancy.
没人知道巴西有多少人已被感染，但CDC估计感染人数在50万到150万之间。据巴西卫生部门透露，目前已有3500例先天性小头症病例。1月15日，美国夏威夷州卫生署(Hawaii State Health Department)报告称，一名感染兹卡病毒的小头症新生儿在瓦胡岛出生，这是美国的首例此类病例。婴儿的母亲怀孕期间曾在巴西居住。
Knowledge is evolving, but as of Jan. 15, the C.D.C . had issued Alert Level 2 Warnings (“Increased risk in defined settings or associated with specific risk factors”) for Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela and Puerto Rico. The agency did not mention Africa or Asia in connection with the Zika virus, but warnings about the dangers of other mosquito-borne illnesses are already in effect in those regions.
Pregnant women, in no matter which trimester, should talk to their doctors if they must travel to countries where Zika infections have been found, and if the trip is not essential, they should consider postponing it. Women who are trying to become pregnant are also at risk, and should discuss their travel plans and the risks of the Zika infection with their health care providers. All travelers should strictly follow the routines that will prevent mosquito bites.
Aedes mosquitoes flourish seasonally in large areas in the United States, and year-round in most of Florida and parts of Texas and California, so travelers who are infected abroad and return to these areas could spread the illness.
Sexual transmission of the virus may also be possible. In 2011, researchers found that a scientist who had contracted the Zika virus while working in Senegal transmitted it to his wife after his return home to Colorado, almost certainly through sexual intercourse. And in 2015 the virus was found in the sperm of a 44-year-old man in Tahiti. There is also at least a theoretical risk of transmission through blood transfusions.