Zika and Two Other Mosquito-Borne Viruses That Are Threatening the U.S.
What is causing the viral threat?
The dengue, chikungunya and Zika viruses are primarily spread by two species of mosquito: Aedes aegypti, commonly known as the yellow fever mosquito; and Aedes albopictus, commonly known as the Asian tiger mosquito.
The Zika virus has been found in semen, but there has been only one documented case of semen infecting another person. The Zika virus has not been found in breast milk.
Climate change is fueling the northward spread of the mosquitoes in the U.S. While only 16% of the United States has a climate ideal to the sustainability of the mosquitoes, the CDC predicts the nearly 50% of the Unites States will have just such an ideal climate by the end of the 21st century.
Pesticide resistance is also spurring increased populations of disease carrying mosquitos. The US NIH published a study which found "that USA populations are broadly susceptible to currently available larvicides and adulticides. Unexpectedly, however, we found significant resistance to DDT in two Florida populations and in a New Jersey population. We also found resistance to malathion in Florida and New Jersey and reduced susceptibility to the IGRs pyriproxyfen and methoprene."
The Zika virus is spreading northward
The Zika virus, which originated in Africa, has spread to southeast Asia, some Pacific and Caribbean islands, and the Americas.
As of August 2016, Florida was reporting many cases of locally acquired transmissions. The American territories of Puerto Rico, American Samoa, and the US Virgin Islands are reporting many Zika cases that have been locally transmitted. The CDC does expect the virus to spread into every area the yellow fever and Asian tiger mosquito are now indigenous.
The World Health Organization (WHO) has issued a warning that the Zika virus will continue to spread through North, Central and South America and surrounding islands:
"Zika is a mosquito-borne virus that is new to the Americas. Since Brazil reported the first cases of local transmission of the virus in May 2015, it has spread to 21 countries and territories* of the Americas (as of 23 January 2016).
There are two main reasons for the virus's rapid spread: (1) the population of the Americas had not previously been exposed to Zika and therefore lacks immunity, and (2) Aedes mosquitoes—the main vector for Zika transmission—are present in all the region's countries except Canada and continental Chile."
Zika cases in the US as of August 2016
Does Zika cause microcephaly in babies?
Although severe cases of Zika virus infection rarely require hospitalization, concern was raised when a possible link to microcephaly in newborns was discovered in Brazil. New cases of microcephaly have increased from a few hundred to over 3500 in just one year.
The virus has been detected in the amniotic fluid of women pregnant with a microcephalic babies. In two of the babies who died shortly after birth, the Zika virus was present in the brain tissue.
The link between Zika and microcephaly needs further study but until then then US CDC has issued a travel alert for women:
- Pregnant women in any trimester should consider postponing travel to the areas where Zika virus transmission is ongoing. Pregnant women who do travel to one of these areas should talk to their doctor or other healthcare provider first and strictly follow steps to avoid mosquito bites during the trip.
- Women trying to become pregnant who are thinking about becoming pregnant should consult with their healthcare provider before traveling to these areas and strictly follow steps to prevent mosquito bites during the trip."
A woman may be able to have the Zika virus detected earlier in her pregnancy. Read about it at NPR.
Zika has been in Africa and Asia for decades without a noticeable increase in microcephalic babies. One theory, briefly explained in the video below, holds that most women on those continents get infected with the virus before puberty. They are then immune to another reinfection when they become pregnant.
A fascinating video on the Zika virus
Symptoms of the Zika virus
- Joint pain
- Swelling of hands and feet
- Low fever
- Skin rash with raised bumps
- Headaches with pain behind the eyes.
- Non-contagious conjunctivitus (pink eye) without discharge
- Muscle pain
- Digestive disorders
At this time there is no vaccine or antiviral treatment for the Zika virus.
The spread of the Zika virus
The name chikungunya, which means "to become contorted”, is derived from the Kimakonde language of the Makonde people of Africa. Chikungunya refers to the stooped appearance of infected people with severe joint pain.
In 2014, chikungunya disease cases were reported among U.S. travelers returning from affected areas in the Americas and local transmission was identified in Florida, Puerto Rico, and the U.S. Virgin Islands.
Symptoms of Chikungunya
- Sudden severe joint pain
- Sudden onset of fever
- Nausea and vomiting
- Muscle pain
Joint pain can be acute in the initial days of an infection, though most pain disappears after 10 days. Approximately 10% of sufferers may develop chronic joint pain which can be debilitating and persist for months.
When the symptoms of an infection are mild, many people are not aware they have contracted the virus. Serious complications are uncommon, but the chikungunya virus can contribute to death in elderly people.
There are no antiviral medicines or vaccines available to treat chikungunya.
Dengue fever was once known as break-bone fever due to the intense pain in joints and bones which made the patient feel as if his bones were breaking.
The World Health Organization estimates 40% of the world's population is at risk from dengue and approximately 12,000 people die of it every year.
In the mid 20th century, dengue fever was thought to be eradicated in the US, but it is again making an unwelcome appearance in some states. Outbreaks have occurred in Florida, Hawaii, and Texas.
Because there are 4 distinctive dengue viruses, a person could conceivably contract all four varieties during his lifetime. Dengue is a leading cause of illness and mortality in tropical and subtropical areas of the world.
Symptoms of Dengue
- High fever occurring with at least two other symptoms
- Severe headache
- Muscle pain
- Severe pain behind the eyes
- Joint and bone pain
- Mild bleeding from nose or gums
- Easy bruising or small purple spots on skin
Symptoms of severe dengue (Dengue hemorrhagic fever)
Symptoms begin after the fever starts to subside, generally after a three to seven days.
Go immediately to an emergency room if you develop any of the symptoms:
- Severe abdominal pain or persistent vomiting
- Red spots on the skin
- Bleeding from the nose or gums
- Vomiting blood
- Swollen abdomen
- Black, tarry stools (feces, excrement)
- Drowsiness or irritability
- Pale, cold, or clammy skin
- Difficulty breathing
Severe dengue may lead to failure of the circulatory system due to internal blood loss. Without medical treatment, shock and possibly death can follow.
Older children and adults generally suffer from more severe infections then young children.
Mortality can be reduced with rapid medical intervention. Currently, there is no vaccine or antivirals available to prevent or treat dengue fever.
How concerned are you with these viruses?
What can we do?
With no vaccines or antiviral drugs capable of combating these diseases, prevention is the best answer.
- Many municipalities routinely spray for mosquitoes, which helps slow the spread of the disease.
- Individuals can make it harder for the mosquitoes to breed by removing any sources of standing water. Old tires, flower pots, empty buckets and puddles can be used as a mosquito breeding ground.
- Wear pants and long sleeved shirts.
- Apply mosquito repellent on exposed skin.
- Stay indoors when mosquitoes are most active.
- Fix any screens or windows which may allow mosquitoes to enter your home.
- WHO: Zika virus to spread to much of Americas - Al Jazeera English
World Health Organization foresees outbreak of mosquito-borne virus throughout the Americas, prompting travel warnings.
- Climate Change and Range Expansion of the Asian Tiger Mosquito (Aedes albopictus) in Northeastern US
Expansion of tiger mosquitoes
- chikungunya fever | disease | Britannica.com
Chikungunya fever, viral disease transmitted to humans by infected mosquitoes that is characterized by fever, headache, rash, and severe joint and muscle pain.
- Centers for Disease Control and Prevention
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© 2016 Gable Rhoads