How a bloodsucker transmits the Zika virus
The Aedes aegypti mosquito is the perfect vector for spreading the virus. It picks up the virus from a human, then can infect another person as it injects saliva from its tiny syringe-like proboscis.
Mosquitoes are measured by wing length. The yellow fever mosquito, Aedes aegypti, has wings that are, at most, 1/8 inch long.
Capillaries
Seeking a blood meal
As she probes for a blood vessel, a female mosquito saws her proboscis back and forth under the skin. She injects saliva, which acts as an anesthetic and prevents blood from clotting once she strikes a capillary.
Midgut
Infecting the vector
After piercing a vessel, the mosquito pumps blood into her midgut. Should her host be infected with Zika, the blood will contain tiny virus particles, each less than 1/100th the diameter of a red blood cell.
Zika virus
particle
Diameter:
50 nanometers
Edge of red blood cell
7,000 nanometers
Hemolymph
Heart
Salivary
glands
Passing it on
Viruses migrate out of the gut and into the insect’s body cavity, which is filled with hemolymph, or insect blood, which is pumped throughout the body cavity by a long, tubular heart. Viruses ultimately penetrate the saliva glands, where they are poised to be injected into another person.
Mosquitoes are measured by wing length. The yellow fever mosquito, Aedes aegypti, has wings that are, at most, 1/8 inch long.
Seeking a blood meal
As she probes for a blood vessel, a female mosquito saws her proboscis back and forth under the skin. She injects saliva, which acts as an anesthetic and prevents blood from clotting once she strikes a capillary.
Capillaries
Infecting the vector
Midgut
After piercing a vessel, the mosquito pumps blood into her midgut. Should her host be infected with Zika, the blood will contain tiny virus particles, each less than 1/100th the diameter of a red blood cell.
Zika virus particle
Diameter:
50 nanometers
Edge of red blood cell
7,000 nanometers
Hemolymph
Passing it on
Heart
Viruses migrate out of the gut and into the insect’s body cavity, which is filled with hemolymph, or insect blood, which is pumped throughout the body cavity by a long, tubular heart. Viruses ultimately penetrate the saliva glands, where they are poised to be injected into another person.
Salivary
glands
Zika virus particle
Diameter: 50 nanometers
Mosquitoes are measured by wing length. The yellow fever mosquito, Aedes aegypti, has wings that are, at most, 1/8 inch long.
Edge of red blood cell
7,000 nanometers
Midgut
Hemolymph
Heart
Salivary
glands
Capillaries
Passing it on
Seeking a blood meal
Infecting the vector
As she probes for a blood vessel, a female mosquito saws her proboscis back and forth under the skin. She injects saliva, which acts as an anesthetic and prevents blood from clotting once she strikes a capillary.
After piercing a vessel, the mosquito pumps blood into her midgut. Should her host be infected with Zika, the blood will contain tiny virus particles, each less than 1/100th the diameter of a red blood cell.
Viruses migrate out of the gut and into the insect’s body cavity, which is filled with hemolymph, or insect blood, which is pumped throughout the body cavity by a long, tubular heart. Viruses ultimately penetrate the saliva glands, where they are poised to be injected into another person.
The differences between mosquitoes
Scientists say Aedes aegypti is the main transmitter of the Zika virus, but other types of mosquitoes may be contributing as well. The similar-looking Aedes albopictus, which thrives in more temperate climates, is a prime suspect. One challenge with eradicating these mosquitoes is that their eggs can withstand months without water, then can hatch when water returns.
Aedes aegypti
Primary carrier of Zika
Aedes albopictus
Suspected secondary carrier
Common name
Yellow fever mosquito
Common name
Asian tiger mosquito
Identifying traits
Dark and small (4-7mm long) with white-banded legs and a silvery lyre-shaped pattern on its thorax
Identifying traits
Also dark and similar in size (2-10mm) with white-banded legs and a silvery lengthwise stripe down its thorax
Region
Prefers to live among humans, especially in urban areas, in the tropics and subtropics
Region
Can live in temperate regions but prefers areas with thick vegetation
Habitat
Lives indoors and outdoors, preferably in shade
Habitat
Lives and bites mostly outdoors
Breeding
Prefers to lays eggs in manmade containers of standing water such as empty pots, buckets and pet dishes
Breeding
Likes to lay eggs in standing water in treeholes but will also lay them in old tires and other manmade containers as well
Biting habits
Bites humans, sometimes multiple times, usually in daytime
Biting habits
Feeds in daytime but targets animals as well as people, so it is less effective at transmitting viruses between people
Lifespan
2–4 weeks
during which a female can produce up to five batches of eggs
Lifespan
30-40 days
during which a female can produce up to four batches of eggs
Travel habits
Weak flier; rarely travels more than 150 feet from where it hatches
Travel habits
Also a weak flier and may never leave its original habitat
Origin
Africa. Likely came to Americas on ships
Origin
Eastern Asia and several Pacific Islands
Examples of viruses it carries
Dengue, chikungunya, yellow fever
Examples of viruses it carries
Dengue, Eastern equine encephalitis
Serious conditions linked to Zika
For most people, a Zika infection is not a big deal. Only 1 in 5 will get sick, and those who do tend to have a few days of fever, rash and other mild symptoms. The problem is that areas affected by the Zika outbreak are seeing an unusual rise in some serious conditions, and evidence points to the virus as the cause.
Zika
First identified in humans in 1952, it is very similar to viruses that cause dengue, West Nile and yellow fever.
COULD AFFECT:
Pregnant women or women
trying to become pregnant
Microcephaly
Microcephaly means a baby’s head is smaller than expected and usually
indicates that the brain didn’t develop properly. Many different things can cause microcephaly. Health officials say the Zika link is strong, and the virus appears to cause the most harm early in the pregnancy.
Other birth defects
Other birth defects may be associated with the Zika virus as well, including some that led to stillbirth or death
shortly after birth. Miscarriages have been reported in women who have had Zika, but it is not known if the virus
contributed to the miscarriages.
COULD AFFECT:
Anyone
Guillain-Barré syndrome
The body’s immune system attacks
protective sheaths around nerve cells, causing weakness and paralysis. An uptick in cases occurs after some
outbreaks of viral illnesses, including flu. It is fatal about 5 percent of the time, according to the WHO.
Zika
First identified in humans in 1952, it is very similar to viruses that cause dengue, West Nile and yellow fever.
COULD AFFECT:
COULD AFFECT:
Pregnant women or women
trying to become pregnant
Anyone
Microcephaly
Guillain-Barré syndrome
The body’s immune system attacks protective sheaths around nerve cells, causing weakness and paralysis. An uptick in cases occurs after some outbreaks of viral illnesses, including flu. It can be fatal. It is fatal about 5 percent of the time, according to the WHO.
Microcephaly means a baby’s head is smaller than expected and usually indicates that the brain didn’t develop properly. Many different things can cause microcephaly. Health officials say the Zika link is strong, and the virus appears to cause the most harm early in the pregnancy.
Other birth defects
Other birth defects may be associated with the Zika virus as well, including some that led to stillbirth or death shortly after birth. Miscarriages have been reported in women who have had Zika, but it is not known if the virus contributed to the miscarriages.
Zika
First identified in humans in 1952, it is very similar to viruses that cause dengue, West Nile and yellow fever.
COULD AFFECT:
COULD AFFECT:
Pregnant women or women trying to become pregnant
Anyone
Other birth defects
Microcephaly
Guillain-Barré syndrome
The body’s immune system attacks protective sheaths around nerve cells, causing
weakness and paralysis. An uptick in cases occurs after some outbreaks of viral illnesses, including flu. It is fatal about 5 percent of the time, according to the WHO.
Other birth defects may be associated with the Zika virus as well, including some that led to stillbirth or death shortly after birth. Miscarriages have been reported in women who have had Zika, but it is not known if the virus contributed to the miscarriages.
Microcephaly means a baby’s head is
smaller than expected and usually indicates that the brain didn’t develop properly. Many different things can cause microcephaly. Health officials say the Zika link is strong, and the virus appears to cause the most harm early in the pregnancy.
How do you get Zika?
The virus can be transmitted through sex, but it is usually carried person-to-person through Aedes aegypti mosquitoes. In a few cases, mothers have passed Zika to newborns. Read more.
The predicted distribution of Aedes aegypti mosquitoes based on a statistical model.
Probability of occurrence
Low
High
Jan.
isotherm
10°C
July
isotherm
10°C
The contour lines of the January and July isotherms indicate the potential geographic limits of the Northern and Southern hemispheres for year-round survival of A. aegypti.
Probability of occurrence
Low
High
10°C
January
isotherm
July
isotherm
10°C
The contour lines of the January and July isotherms indicate the potential geographic limits of the Northern and Southern hemispheres for year-round survival of A. aegypti.
10°C
January
isotherm
Probability of occurrence
Low
High
July
isotherm
The contour lines of the January and July isotherms indicate the potential geographic limits of the Northern and Southern hemispheres for year-round survival of A. aegypti.
10°C
Researchers writing in the Lancet calculated that about 200 million people in the United States live in areas where Zika could spread in warm months and that another 22.7 million live in subtropical areas where it could spread year-round.
Where is it?
The current outbreak began in May 2015 in Brazil, and the virus is being transmitted locally by mosquitoes in more than three dozen other countries and territories. The continental United States is not included in that number because confirmed U.S. cases occurred after travelers were bitten abroad. The CDC recommends that pregnant women avoid traveling to these countries unless they will be at elevations above about 6,500 feet, which is higher than Zika-carrying mosquitoes generally live.
Active Zika Virus Transmission
What does it feel like?
A Zika infection is diagnosed by a blood test and has some of the same symptoms as early dengue fever, though only 20 percent of those infected will have any symptoms at all. Symptoms typically last two to seven days.
Common symptoms:
- Fever
- Rash
- Joint pain
- Conjuctivitis (pinkeye)
Rarer symptoms:
- Muscle pain
- Headache
How do you treat it?
There is no Zika-specific medication, but you can treat the symptoms:
- Rest
- Drink plenty of fluids to prevent dehydration
- Take a pain reliever/fever reducer such as acetaminophen, but do not take aspirin or nonsteroidal anti-inflammatories (NSAIDS) such as ibuprofen or naproxen until dengue is ruled out.
- Once you recover from a Zika infection, you are immune, at least for a while. But scientists don’t know how long that immunity lasts.
How do you prevent it?
Any vaccine is still months — or even years — away, so the key is not to get bitten in the first place. If you’re in mosquito country, use insect repellent outdoors and wear protective clothing with long sleeves and long pants, especially during daytime when these mosquitoes are out and eager to bite.
Contraceptive prevalence in countries with Zika
Many countries in Latin America and the Caribbean where Zika has been locally transmitted have restrictive abortion policies, and contraceptives in these areas are often hard to obtain.
Least restrictive: Abortion is legal
World avg.
64
Guyana
44.8%
Mexico
72.6
40
60
80%
Contraceptive
prevalence rate
Some restrictions: Abortion only
legal for certain reasons or to
save a woman’s life
Colombia
78.2
Bolivia
62.5
Barbados
60.3
Panama
61.3
Restrictive: Abortion only legal to
save a woman’s life and/or to
preserve her health
Costa Rica
78.9
Brazil
79
Ecuador
72.6
Highly restrictive: Abortion legal
only to save a woman’s life
Haiti
37.8
Suriname
51.8
Venezuela
70
Honduras
72.7
Guatemala
57.2
Paraguay
77.4
Most restrictive: Abortion is illegal
El Salvador
70.7
D.R.
71.8
Nicaragua
79.5
Least restrictive: Abortion is legal
World avg.
64
Guyana
44.8%
Mexico
72.6
40
60
80%
Contraceptive
prevalence rate
Some restrictions: Abortion only
legal for certain reasons or
to save a woman’s life
Barbados
60.3
Colombia
78.2
Bolivia
62.5
Panama
61.3
Restrictive: Abortion only legal
to save a woman’s life and/or
to preserve her health
Ecuador
72.6
Costa Rica
78.9
Brazil
79
Highly restrictive: Abortion legal only to save a woman’s life
Haiti
37.8
Suriname
51.8
Venezuela
70
Guatemala
57.2
Honduras
72.7
Paraguay
77.4
Most restrictive: Abortion is illegal
El Salvador
70.7
Dom. Rep.
71.8
Nicaragua
79.5
Note: Contraceptive prevalence rates are of any method, and data is as of 2015. Abortion policies are as of 2013.