Health officials in Brazil have warned of an \u0022unprecedented situation\u0022 and are even urging women in some states to avoid getting pregnant as they\u0026#039;ve linked a rise in babies born with a serious birth defect to a mosquito-borne viral disease.The virus in question is Zika, which is transmitted by the Aedes aegypti mosquito.\u0026nbsp; That mosquito also carries dengue and chikungunya.As the World Health Organization explains, Zika fever \u0022is usually mild with symptoms that can last between two and seven days.\u0022 Those symptoms may include a mild fever, rash, and headaches. But the disease is now being linked in Brazil to microcephaly in newborns, a neurological condition in which the head is very small because of an abnormally developed brain.In Brazil this year, there\u0026#039;s been a massive rise in the number of cases of microcephaly linked to the virus, prompting six states to declare a state of emergency.\u0026nbsp; While last year there were a reported 147 cases of microcephaly, there have been over 2,700 cases of babies born with microcephaly this year, with a 16-percent increase reported just this week.\u0026nbsp;According to figures released Dec. 1 by the Pan American Health Organization, there\u0026#039;s been \u0022a twentyfold increase [in microcephaly] in comparison to the rate observed in previous years.\u0022Brazil\u0026#039;s Health Ministry says over 1.5 million people could contract the Zika virus by the year\u0026#039;s end; other countries in the Americas that have reported local Zika transmission include Colombia, Venezuela, Panama, and as far north as Mexico.\u0022This is probably the largest outbreak of Zika ever recorded,\u0022 the Wall Street Journal quotes Ann Powers, acting chief of the arboviral diseases branch at the Atlanta-based Centers for Disease Control and Prevention, as saying. \u0022There’s a lot of concern about what it means, what the implications are, and what we can potentially do for containment and control.\u0022From CNN:When the cases of microcephaly started to soar last month, doctors noticed they coincided with the appearance of the Zika virus in Brazil. They soon discovered that most of the affected mothers reported having Zika-like symptoms during early pregnancy -- mild fever, rash and headaches.On November 28, Brazil\u0026#039;s Health Ministry announced that during an autopsy it had found the Zika virus in a baby born with microcephaly, establishing a link between the two.\u0022This is an unprecedented situation, unprecedented in world scientific research,\u0022 the ministry said on its website.The Washington Post adds:Until a few years ago, human infections with the virus were almost unheard of. Then, for reasons scientists can\u0026#039;t explain but think may have to do with the complicated effects of climate change, it began to pop up in far-flung parts of the world. In 2007, it infected nearly three-quarters of Yap Island\u0026#039;s 11,000 residents. In 2013, Zika showed up in Tahiti and other parts of French Polynesia and was responsible for making an estimated 28,000 people so ill they sought medical care. It arrived in Brazil in May, where tens of thousands have fallen ill.The country is also dealing with a dengue epidemic. \u0022One of the reasons is climate change, according to experts.\u0022 NPR reports. \u0022A harsh drought has been affecting Brazil, so people are storing water on their rooftops.\u0026nbsp; The Aedes aegypti loves to breed in standing water in urban environments.\u0022Researchers with the United Nations University last year also pointed to how climate change could worsen dengue\u0026#039;s threat.\u0026nbsp; \u0022Changes to climate could result in increased exposure and pose a serious threat to areas that do not currently experience endemic dengue,\u0022 their report said.