The Zika virus made news in the United States two weeks ago when the first case of brain damage linked to the virus was reported in Hawaii. The Hawaii State Department of Health reported that a baby born in an Oahu hospital with microcephaly had been infected with the Zika virus. The Centers for Disease Control and Prevention (CDC) confirmed the infection. The mother of the baby had lived in Brazil in May last year and had probably been infected with the virus by a mosquito early in her pregnancy at that time.
Said Dr, Sarah Park, the state epidemiologist in Hawaii, in a statement, “We are saddened by the events that have affected this mother and her newborn. This case further emphasizes the importance of the C.D.C. travel recommendations released today.”
Two weeks ago, the CDC advised pregnant women to postpone traveling to 13 Latin American or Caribbean countries and Puerto Rico in which mosquitoes are spreading the Zika virus. The CDC also advised that women considering pregnancy consult a health care professional before traveling to countries with Zika cases. All travelers should also avoid mosquito bites by covering exposed skin long-sleeved shirts and long pants; using EPA-registered insect repellents containing DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535; using permethrin-treated clothing and gear; and staying and sleeping in screened-in or air-conditioned rooms.
Commented Dr. Lyle R. Petersen, chief of vector-borne diseases for the CDC, on the travel health notice, “We believe this is a fairly serious problem. This virus is spreading throughout the Americas. We didn’t feel we could wait.”
The Zika virus causes Zika, a disease spread to humans primarily through the bite of an infected Aedes species mosquito. Only one in five individuals infected with the virus will become ill, and the illness is usually mild. The most common symptoms of the disease include fever, rash, joint pain, and conjunctivitis (red eyes). Severe symptoms requiring hospitalization are uncommon. Many people infected with the Zika virus are unaware of the infection.
More alarmingly, the Zika virus has been linked to a birth defect called microcephaly. Microcephaly is a birth defect in which the head of a baby is smaller than expected when compared to babies of the same sex and age. Affected babies often have smaller brains that might properly not developed properly during pregnancy or have stopped growing after birth. Microcephaly has been linked with other problems including seizures, developmental delay, intellectual disability, movement and balance problems, feeding problems, hearing loss, and vision problems. Microcephaly is an uncommon condition, affecting an estimated two babies per 10,000 live births to twelve babies per 10,000 live births in the Unites States. Microcephaly is a lifelong condition with no known treatments or cures.
Although the association between the Zika virus and microcephaly is not yet conclusive, researchers are studying the possible link. That Zika may cause microcephaly in babies made headlines in October when doctors in Pernambuco State of Brazil noticed a surge in cases of microcephaly. The country normally sees about 150 cases of the birth defect each year. Since October, more than 3,500 have been reported in Brazil.
Widespread in Africa and Southeast Asia, the Zika virus was first discovered in monkeys in the Zika Forest in Uganda in 1947. The Asian strain of the virus was detected moving across the South Pacific in 2007 when a large outbreak occurred on Yap Island that year. The virus reached Easter Island off the coast of Chili by late 2014. The virus reached Brazil in May 2015, and epidemiologists estimate that more than 1.5 million Brazilians have been infected.
Researchers in Brazil and the United States have found the Zika virus in the brain tissue and amniotic fluid from babies who died prenatally or were born with microcephaly The Zika virus is related to the dengue, yellow fever, and West Nile viruses. Although all three viruses can cause health problems, none have been linked to birth defects like microcephaly. The Zika virus is not related to rubella or cytomegalovirus, both of which can cause microcephaly. Genetic defects and prenatal alcohol exposure can also cause the birth defect. Scientists thus do not yet know if or how the Zika virus crosses the placenta and damages fetal brains. Researchers also do not yet know whether the Zika virus alone causes microcephaly or if the birth defect occurs only if the mother has a previous infection such as with the dengue virus.
The Zika virus has also been linked to Guillain-Barre syndrome (GBS), a rare disorder in which the immune system damages nerve cells, causing muscle weakness and sometimes paralysis. The Brazil Ministry of Health has also reported an increase in GBS cases, and the CDC is working to deteremine whether Zika and GBS are related, but determining if any particular pathogen caused the syndrome is difficult.
Experts expect Zika to begin spreading in the United States as the weather warms in the spring and summer. More than a dozen isolated cases have been reported in the continental United States including one in Texas, but so far all cases have occurred in travelers who had just returned from overseas. No local transmission has yet been found. Dr. Erin Staples, a CDC epidemiologist, expects Zika to follow the same pattern as other mosquito-borne viruses like dengue and chikungunya with large outbreaks in Puerto Rico followed by smaller ones in Florida, Gulf Coast states, and Hawaii.
No vaccine yet exists for Zika, but the National Institute of Allergy and Infectious Diseases has been working on one for the past month, reports Dr. Anthony S. Fauci, the director of the institute. Because the disease is closely related to yellow fever and Japanese encephalitis, for which vaccines exists, developing one for Zika should not prove difficult. A vaccine could be ready for emergency use before the end of the year, says one of the lead developers.
In the meanwhile, pregnant women and women considering pregnancy should avoid nonessential travel to Zika-affected areas. A leading Brazilian health official also suggested that women in the affected regions postpone having babies.
References
Facts About Microcephaly: http://www.cdc.gov/ncbddd/birthdefects/microcephaly.html
Hawaii Baby with Brain Damage Is First U.S. Case Tied to Zika Virus: http://www.nytimes.com/2016/01/17/health/hawaii-reports-baby-born-with-brain-damage-linked-to-zika-virus.html
To Protect Against Zika Virus, Pregnant Women Are Warned About Latin American Trips: http://www.nytimes.com/2016/01/16/health/zika-virus-cdc-pregnant-women-travel-warning.html
Travel Health Notices: http://wwwnc.cdc.gov/travel/notices
What Would It Take to Prove the Zika–Microcephaly Link: http://www.scientificamerican.com/article/what-would-it-take-to-prove-the-zika-microcephaly-link/
Zika Vaccine May Be Ready for Emergency Use This Year: Developer: http://www.reuters.com/article/us-health-zika-interview-idUSKCN0V704J
Zika Virus: http://www.cdc.gov/zika/
Zika Virus Disease Q & A: http://www.cdc.gov/zika/disease-qa.html
Image Credits
Female Aedes Aegypti Mosquito: https://www.flickr.com/photos/usdagov/8412924296/ (CC BY 2.0)
Baby with Microcephaly and Baby with Typical Head Size: http://www.cdc.gov/ncbddd/birthdefects/images/microcephaly-comparison-350px.jpg
Kokuvi (Seventeen-Year-Old with Microcephaly) and Me: https://www.flickr.com/photos/ahstillwell/1076280246/ (CC BY-NC-ND 2.0)
