KNOWNS AND UNKNOWNS ABOUT THE ZIKA VIRUS EPIDEMIC
The Zika virus is transmitted by container breeding mosquito species that are found in tropical and subtropical regions across the globe. Aedes aegypti is the principal vector for the Zika virus but studies indicate that Aedes albopictus can also be an effective carrier for the virus. The virus was first isolated from a captive rhesus monkey in from the Zika Forest in Uganda in 1947. The first confirmed human infections were in 1952 in Uganda and Tanzania. The virus is known to cause dengue-like symptoms that may include fever, skin rashes, conjunctivitis, muscle and joint pain, malaise, and headache which can last between 2-7 days.
Over the course of the next several decades, the virus spread from Africa to Asia and on to French Polynesia. Limited attention was given to the virus until it recently arrived in Brazil. There is no clear confirmation as to when Zika virus actually reached South America but recent genomic studies indicate that the virus likely spread to the Americas between May 2013 and December 2013. The number of travelers arriving in Brazil from Zika-affected countries increased from 3,775 per month in early 2013 to 5,754 per month in 2014. The virus was thought to be harmless until October 2015 when researchers reported seeing unusually high rates of neurological disorders in Brazilian newborns. These babies were born with unusually small heads, a condition known as microcephaly. Several other medical conditions such as rubella (measles), toxoplasmosis, and cytomegalovirus (one of the herpes viruses) are also known to cause microcephaly, but Brazilian doctors noted unusually high numbers of microcephaly since the epidemic of Zika virus began. Analysis has indicated that among the 15 states that have reported Zika cases, microcephaly has been observed in 2.8 out of 10,000 births whereas the disorder is only expressed in 0.6 per 10,000 births in the four Brazilian states that do not have confirmed Zika infections.
Northeastern Brazil shows a considerably higher incidence of cases at 14.6 per 10,000 cases in the State of Pernambuco followed by Paraiba State with 10.6 cases per 10,000 births. An increasing number of stillborn babies and aborted fetuses with microcephaly are also being reported. Brazil’s ministry of health reports more than 6000 suspected cases of microcephaly from November 2015 to March 2016 alone. Only about 2200 of these cases have been investigated – 854 of those confirmed as microcephaly via laboratory test and 97 of those cases including confirmed Zika infections in the mother.
Zika virus infections are also suspected to cause Guillain–Barré Syndrome, a condition that causes the immune system to attack the peripheral nervous system. Severe cases of this rare autoimmune disorder may cause paralysis. Far more common is muscle weakness beginning with the extremities. Most of the states in Brazil that report higher incidences of Zika virus infections are also reporting higher than normal instances of Guillain–Barré Syndrome. Some states report 517% more cases than normal.
On April 13, 2016, the Centers for Disease Control (CDC) confirmed the link between Zika virus and other severe fetal brain defects and has issued travel warnings for pregnant women traveling to Brazil. In March 2016, the Washington Post quoted Anthony Costello, who heads WHO’s department of maternal, newborn, child and adolescent health, as saying the organization expects “more than 2,500 cases will emerge of babies with brain damage and clinical signs of microcephaly,” in Brazil, if current rates continue.
Mosquito control still remains the best method to combat this virus. Container mosquitoes may develop in small, often hidden containers that can carry less than one liter of water, containers such as refuse, flower vases, and toys etc. Thousands of adult mosquitoes can develop in a container that holds just a palm full of water.