In 2009, it was H1N1. In 2014 and 2015, it was Ebola. Now it is Zika. It seems every few years a virus emerges that has the world’s attention and concern. This year’s virus has been in the headlines since early 2016 and is called the Zika virus.
It is a virus transmitted by Aedes mosquitoes, the same type of mosquito that transmits dengue, chikungunya, and yellow fever. It was first identified in Uganda in 1947 in rhesus monkeys and then later in humans in 1952 in Uganda and the United Republic of Tanzania. One in five people infected with Zika virus become ill. Those with Zika virus disease usually have a mild fever, skin rash, and conjunctivitis (pinkeye). These symptoms typically last for two to seven days. It is uncommon for the disease to cause hospitalization and very rare for those infected to die. Currently there is no treatment or vaccine; the best form of prevention is to avoid being bitten by mosquitoes.
Zika virus is often found in Africa, the Americas, Asia, and the Pacific. The first few outbreaks were reported from Yap (in the Pacific) in 2007, French Polynesia in 2013 (also in the Pacific), and Brazil and Colombia and Cape Verde (Africa) in 2015. More than 13 countries in the Americas have reported Zika virus infections showing that the virus can had explosive expansion geographically. No cases have been transmitted in the United States and it is doubted that Zika will spread in the US (most likely there will be isolated cases from returning travelers), but some returning travelers from Zika-infected areas have had the infection. For the recent increase of Zika virus infection, which was historically rare, virologists think increased international travel and climate change have played a role.
On January 29th, 2016 the Centers for Disease Control and Prevention (CDC) released a report about the possible connection between Zika virus and microcephaly, a birth defect where a baby’s head is very small, often leading the baby to have a smaller brain that did not develop properly. In northeastern Brazil in September 2015, after the start of an outbreak early in the year, health officials were receiving reports from physicians regarding an increase in the cases of microcephaly. In addition, Zika virus RNA was identified in the amniotic fluid of two women whose fetuses had microcephaly. In response to this discovery, the Brazilian Society of Medical Genetics established the Zika Embryopathy Task Force (SBGM-ZETF). The goal of SBGM-ZETF was to review all cases of microcephaly whose mothers may have had Zika virus infection during their pregnancy. The task force evaluated 35 babies born with microcephaly and found that in the first or second trimester, 26 (74%) of the mothers reported a rash. All mothers were confirmed to have travel to areas were Zika virus was present. CDC also tested samples of two pregnancies that ended in miscarriage and from two infants with microcephaly that died after birth. All four cases were from Brazil and positive for Zika virus infection, the same strain that is in Brazil now. All four of the mothers had a rash during their pregnancies. However, more scientific testing is required to confirm a relationship between Zika virus and microcephaly.
In response to this explosive outbreak, the CDC has developed a test that in the first week of illness can confirm Zika. A difficulty that the CDC and other scientists are finding troubling is finding out if a person was previously infected with Zika since the traces of the virus are gone after about a week of infection, but the CDC and private companies are working on tests that can do that. The CDC has also released guidelines to health care providers in the US if they end up caring for infants whose mothers traveled or lived in an area where Zika virus was present during their pregnancy. The CDC has also issued a travel advisory for pregnant women to avoid areas where the virus is circulating. If being in a Zika-affected area is unavoidable for a pregnant woman, the CDC advised the wearing of protective clothing, applying a US Environmental Protection Agency (EPA) approved insect repellant, and sleeping under a mosquito net.
On Monday, the World Health Organization (WHO) announced the Zika virus a public health emergency of international concern. This action has only been taken three times before in 2009, May 2014, and August 2014 for the H1N1 influenza epidemic, a paralyzing form of polio that appeared in Pakistan and Syria, and the Ebola outbreak in West Africa, respectively. This announcement can bring more funding and manpower to fight Zika virus infection. The WHO is currently prioritizing research into Zika virus infection and supporting health officials in efforts to reduce Aedes mosquito populations by eliminating standing water areas. By the end of 2016, the WHO has estimated that up to four million people will become infected with Zika and that a relationship between Zika and microcephaly is suspected even though it hasn’t been scientifically proven.
The outbreaks of Zika virus and Ebola have been compared. Ebola affected almost 30,000 people West African countries while Zika could affect millions of people throughout the Western Hemisphere. Ebola was easier to track since the symptoms are very visible but the problem with tracking Zika virus spread is that most carriers are symptomless. The mosquito that can transmit the virus is found in many parts of the world and with international travel can make the spread of the virus worse.
This relatively quick response by the WHO is most likely because of the way it was criticized in its handling of the 2014 Ebola outbreak. The Ebola outbreak was reported in March 2014 but WHO did not declare a public health emergency of international concern till August 9th. They were criticized for an ineffective response in the important first few months of the outbreaks. Dr. Margaret Chan, WHO’s director general, even admitted “It [Ebola outbreak] overwhelmed the capacity of WHO”.
It seems that the WHO has learned from the past and is now taking early and effective action against Zika virus, which has the chance to spread more than Ebola.