Zika is here to stay, says Dr. Alan Lockwood, emeritus professor of neurology at the University at Buffalo, Buffalo, NY and a senior scientist at Physicians for Social Responsibility, Washington DC. He is the author of The Silent Epidemic and the forthcoming Heat Advisory. Heat Advisory details how climate change is affecting public health, including the increased range of mosquitos carrying the Zika virus, and in this post Dr. Lockwood reflects on the recent discovery of mosquitos carrying the virus found in a small section of Miami.
Hardly a day goes by without another news story about the Zika virus. This is a relatively new virus. It was first identified in the Zika Forest in Uganda in 1947. Originally confined to tropical areas in Africa and Asia, it spread across the Pacific Ocean reaching epidemic levels in the Americas during the last year. Most infections with the virus are mild and may not be noticed. However, after a large number of children with microcephaly were born to Brazilian mothers who had been infected with the virus the fear of this virus rose dramatically. Although these initial reports were treated with the level of caution that is typical of scientists, there is now little doubt that Zika virus infection may cause microcephalus. The relatively recent detailed publication of the brain pathology associated with Zika-induced microcephaly provided additional convincing evidence for the link. The Zika-infected brain was much smaller than normal, malformed, and contained many focal calcifications, evidence of prior injury by the virus. Current research also suggests that Zika virus may cause Gullian Barré Syndrome in adults. This poorly understood but relatively rare disorder is the result of immunological attacks on nerve cells and may occur after a variety of diseases.
Most cases of Zika Disease follow being bitten by an infected mosquito. Most cases are thought to be transmitted by Aedes aegypti mosquitoes. These mosquitoes are active during the daytime, making it more difficult to avoid bites. Other species of the Aedes genus, such as A. albopictus have also been shown to carry the virus. This mosquito has a much wider range than A. aegypti but not as wide as the much more common mosquito Culex quinquefasciatus, better known in the U.S. as the southern house mosquito. Recent reports suggest that this mosquito may also carry the virus. Zika virus has also been isolated from many other mosquitoes, particularly from the Aedes genus, however, it is not known whether they are capable of spreading the disease. If we are lucky, the virus could be a passive passenger on some of these insects. Much more research is needed.
Zika virus can be spread by mechanisms other than the bite of an infected mosquito. These include sexual intercourse and via transfusions with blood from an infected individual who has circulating virus. These reports have led to additional warnings and restrictions placed on blood transfusions.
Early cases of Zika virus infections in the U.S. were mostly related to mosquito bites sustained in areas outside of the country where the disease is much more rampant, such as Brazil. According to the Centers for Disease Control and Prevention, as of July 21, 2016, there were 433 cases among women in the U.S. This all changed, as might be expected, when the Florida Department of Health identified cases of mosquito-transmission of the disease in the Wynwood area of Miami. It is likely that an infected traveler was bitten by a mosquito that then spread the virus secondarily. It is extremely likely that additional locations where mosquitoes have spread the disease in the U.S. will be identified in the future.
The absolute risk for Zika virus infection is still low. However, since this is a new virus and therefore virtually no Americans have any immunity as a result of prior infections, there are concerns among some that without stringent public health measures designed to curb the spread of the disease, many more cases will arise. These infections are virtually certain to include pregnant women who could then give birth to microcephalic children. Microcephaly is a devastating condition. Depending on the degree or severity of the microcephaly, these children are likely to have severe mental retardation that may not be compatible with survival or require lifelong care in skilled nursing facilities.
At present, although trials are underway, there are no vaccines available to prevent the disease and there are no drugs available to treat the infection if it arises. Prevention is critical. Prevention requires a multifaceted approach. Intense measures to eradicate mosquito populations are needed and typically include elimination of standing water, the breeding ground for the mosquitoes, the use of mosquito larvicides, or, in some cases, spraying to kill adult mosquitoes. Personal protective measures are also important and include wearing clothing with long sleeves and pants and the use of mosquito repellants, particularly those containing DEET (N,N-Diethyl-meta-toluamide), and making sure that window screens are intact.
Zika is here to stay. An effective battle against the virus and its horrific effects will be long and expensive. Personal responsibility must be augmented by vigorous actions by local, state, and federal agencies. Climate change is lurking in the background of this fight. Predicted increase in temperature and rainfall in many parts of the nation will favor an expansion of the range of the mosquitoes that carry the disease. This will increase the risk of transmission. This will be a costly battle, but it will not be as costly as doing nothing.