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Short Answers to Hard Questions About Zika Virus
The World Health Organization has declared an international health emergency over the spread of the Zika virus, now known to cause devastating birth defects. The agency expects the virus to spread from northern Argentina to the southern United States by the end of the year, infecting many millions of people. In late July, Florida officials announced what appeared to be the first locally transmitted cases of Zika infection in the continental United States.
The W.H.O. and the Centers for Disease Control and Prevention have urged pregnant women against travel to more than 45 countries in which the Zika virus is spreading, mostly in the Caribbean and Latin America. All pregnant women who have been to these regions should be tested for the infection, health officials have said, and should refrain from unprotected sex with partners who have visited these regions.
The Zika virus has been linked to unusually small heads and brain damage in newborns — called microcephaly — in children born to infected mothers, as well as blindness, deafness, seizures and other congenital defects. In adults, the virus is linked to a form of temporary paralysis, called Guillain-Barré syndrome.
By The New York Times | Sources: Centers for Disease Control and Prevention; Pan American Health Organization
1.
What is the Zika virus?
A tropical infection new to the Western Hemisphere.
The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. Although it was discovered in the Zika forest in Uganda in 1947 and is believed to be common across Africa and Asia, it did not begin spreading widely in the Western Hemisphere until recently — perhaps sometime in 2013, although its presence was not confirmed until May 2015, when it was identified as the “mystery disease” sweeping across northeast Brazil.
Almost no one in the Americas is immune, so it has spread rapidly.
About four in five victims have no symptoms, and those who do usually recover within a week. Common symptoms include a fever rarely higher than 102 degrees, an itchy pink rash, bloodshot eyes, sensitivity to light, headaches and joint pains.
Only female mosquitoes bite people: they need blood to lay eggs, while males drink plant nectar. In the female, the virus travels from the gut to the salivary glands and is injected into the next human victim. When a mosquito bites, it first injects an anti-coagulant saliva so blood does not clog its strawlike proboscis.
Range of the Yellow Fever Mosquito
UNITED
STATES
Atlantic
Ocean
MEXICO
VENEZUELA
PANAMA
COLOMBIA
Pacific
Ocean
ECUADOR
BRAZIL
PERU
BOLIVIA
100%
Probable range
of the yellow
fever mosquito,
Aedes aegypti
PARAGUAY
50%
0%
ARGENTINA
UNITED
STATES
Atlantic
Ocean
MEXICO
VENEZUELA
PANAMA
COLOMBIA
Pacific
Ocean
ECUADOR
BRAZIL
PERU
BOLIVIA
100%
Probable range
of the yellow
fever mosquito,
Aedes aegypti
PARAGUAY
50%
0%
ARGENTINA
UNITED
STATES
Atlantic
Ocean
MEXICO
VENEZUELA
PANAMA
Pacific
Ocean
COLOMBIA
ECUADOR
BRAZIL
PERU
BOLIVIA
100%
Probable range
of the yellow
fever mosquito,
Aedes aegypti
PARAGUAY
50%
ARGENTINA
0%
UNITED
STATES
Atlantic
Ocean
MEXICO
VENEZUELA
PANAMA
COLOMBIA
ECUADOR
Pacific
Ocean
BRAZIL
PERU
BOLIVIA
100%
Probable range
of the yellow
fever mosquito,
Aedes aegypti
PARAGUAY
50%
ARGENTINA
0%
By The New York Times | Source: Moritz U. G. Kraemer et al., eLife Sciences; Simon Hay, University of Oxford
3.
What areas is Zika likely to reach?
Wherever certain mosquitoes go.
Zika is spread by mosquitoes of the Aedes genus, which can breed in a pool of water as small as a bottle cap and usually bite in daytime. The yellow fever mosquito, Aedes aegypti, takes several bites for each blood meal and prefers biting people; it accounts for most Zika infections. This mosquito is common in the United States typically only in Florida and along the Gulf Coast, although it has been found as far north as Connecticut in hot weather.
The Asian tiger mosquito, Aedes albopictus, also can transmit the virus, but not as effectively. It bites many kinds of animals and is found as far north as Maine and Minnesota in summer, and also in Hawaii.
4.
Can the Zika virus be sexually transmitted?
Yes.
Although experts believe that the vast majority of Zika infections are transmitted by mosquitoes, sexual transmission has been reported in 10 countries, including the United States, France, Germany, Italy and New Zealand.
In all known cases as of late June, transmission has been from a man to a woman or to another man, not from a woman to anyone else. The Zika virus has clearly been transmitted by vaginal and anal sex, and possibly by oral sex.
Viral RNA has been found in semen more than two months after symptoms disappeared. Scientists believe the prostate or testes serve as a reservoir, sheltering the Zika virus from the immune system. In at least one case, a man who never had Zika symptoms transmitted it sexually.
Health authorities now recommend that women who are pregnant or trying to become pregnant avoid contact with semen from men who have visited areas where the virus is transmitted. Pregnant women should abstain until they give birth, or should have sex only with partners using a condom.
To reduce the risk of sexual transmission, health authorities recommend that men who have visited areas in which the Zika virus is transmitted by mosquitos and who have had symptoms avoid unprotected sex for six months. Men who have had no symptoms should wait eight weeks.
5.
How might Zika cause brain damage in infants?
Experts aren’t yet certain.
Although it is known that the virus causes brain damage, the mechanism is still being studied. The virus can cross the placenta and attack fetal nerve cells, including some that develop into the brain. The radial glial cells, which form the initial “scaffolding” that guides other fetal brain cells into place, appear particularly vulnerable.
Microcephaly Cases in Brazil
Atlantic
Ocean
VENEZUELA
PANAMA
Pacific
Ocean
COLOMBIA
ECUADOR
BRAZIL
PERU
Recife
BOLIVIA
Microcephaly cases in Brazil
By state, as of March 26
Rio de Janeiro
ARGENTINA
10
100
1,000
10
100
Possible cases
under investigation
Confirmed
cases
Atlantic
Ocean
VENEZUELA
PANAMA
Pacific
Ocean
COLOMBIA
ECUADOR
BRAZIL
PERU
Recife
BOLIVIA
Microcephaly cases in Brazil
By state, as of March 26
Rio de Janeiro
ARGENTINA
10
100
1,000
10
100
Possible cases
under investigation
Confirmed
cases
Microcephaly cases in Brazil
By state, as of March 26
VENEZUELA
COLOMBIA
BRAZIL
PERU
Recife
BOLIVIA
Rio de Janeiro
ARGENTINA
10
100
1,000
10
100
Possible cases
under investigation
Confirmed
cases
Microcephaly cases in Brazil
By state, as of March 26
BRAZIL
Recife
Rio de Janeiro
10
100
1,000
10
100
Possible cases
under investigation
Confirmed
cases
By The New York Times | Source: Brazil’s Ministry of Health
6.
What is microcephaly?
An unusually small head, often accompanied by brain damage.
Babies with microcephaly have unusually small heads. Normally, some degree of microcephaly occurs in 1 in 5,000 to 1 in 10,000 of all births. In roughly 15 percent of cases, a small head is just a small head, with no effect on the infant.
But infection with the Zika virus causes a severe form of microcephaly. The brain may stop growing and be small and smooth, lacking the normal indentations. The long nerves connecting the eyes and ears to the brain may be damaged. Children may suffer from constant seizures or be born with permanently rigid limbs.
Microcephaly can also be caused by other infections of the fetus, including German measles (also known as rubella), toxoplasmosis (a disease caused by a parasite found in undercooked meat and cat feces) and cytomegalovirus.
Microcephaly may also result from alcoholism, drug use or some industrial toxins during pregnancy, or from severe malnutrition of the mother. It can be caused by complications of diabetes and by the genes like those that cause Down syndrome.
There is no treatment for the brain damage.
“There is no way to fix the problem, just therapies to deal with the downstream consequences,” said Dr. Hannah M. Tully, a neurologist at Seattle Children’s Hospital who specializes in brain malformations.
What countries should pregnant women avoid?
United States
Haiti
Dominican Republic
Puerto Rico
Guadeloupe
St. Martin
Martinique
Barbados
U.S. Virgin Islands
Curaçao
Trinadad and Tobago
Atlantic
Ocean
Mexico
Cuba
Jamaica
Guatemala
Honduras
El Salvador
Nicaragua
Costa Rica
Guyana
Suriname
French Guiana
Venezuela
Panama
Colombia
Ecuador
Pacific
Ocean
Brazil
Peru
Areas
pregnant women
should avoid
Bolivia
Paraguay
Argentina
Note: American Samoa, Cape Verde, Tonga and the Marshall Islands should also be avoided.
Haiti
Dominican Republic
Puerto Rico
Guadeloupe
St. Martin
Martinique
Barbados
U.S. Virgin Islands
Curaçao
Trinadad and Tobago
Atlantic
Ocean
Mexico
Cuba
Jamaica
Guatemala
Honduras
El Salvador
Nicaragua
Costa Rica
Venezuela
Guyana
Suriname
French Guiana
Panama
Colombia
Ecuador
Pacific
Ocean
Brazil
Peru
Areas
pregnant women
should avoid
Bolivia
Paraguay
Note: American Samoa, Cape Verde, Tonga and the Marshall Islands should also be avoided.
Argentina
Haiti and Dom. Rep.
Puerto Rico
Guadeloupe
St. Martin
Martinique
Barbados
U.S. Virgin Islands
Curaçao
Trinadad and Tobago
Mexico
Jamaica
Guatemala
Honduras
El Salvador
Nicaragua
Costa Rica
Venezuela
Guyana
Suriname
French Guiana
Panama
Colombia
Ecuador
Pacific
Ocean
Brazil
Areas
pregnant women
should avoid
Bolivia
Note: American Samoa, Cape Verde, Tonga and the Marshall Islands should also be avoided.
Paraguay
Atlantic
Ocean
Mexico
Venezuela
Pacific
Ocean
Colombia
Ecuador
Areas
pregnant women
should avoid
Brazil
Bolivia
Note: American Samoa, Cape Verde, Tonga and the Marshall Islands should also be avoided.
Paraguay
By The New York Times | Sources: Centers for Disease Control and Prevention; Pan American Health Organization
7.
What places should pregnant women avoid?
More than 45 countries and territories, mostly in the Americas and South Pacific.
World health authorities expect the outbreak to eventually reach every place in the Americas where the Aedes aegypti mosquito has previously spread the dengue virus. That includes everywhere from Florida and the Gulf Coast to northern Argentina. Hawaii may be affected as well. Some Pacific Islands are now having outbreaks.
Even within those countries, according to the C.D.C., pregnant women can safely visit areas at altitudes above 6,500 feet because mosquitoes are not normally found there. The latest C.D.C. updates are here.
8.
How do I know if I’ve been infected? Is there a test?
It’s often a silent infection and hard to diagnose.
Only one of five infected people develop symptoms. There is currently no rapid test that can be done in a doctor’s office; tests must be sent to sophisticated laboratories, which delays diagnosis.
The surest way to detect the virus itself is with a blood or urine sample gathered in the first two weeks or less after symptoms appear. Antibody tests can be done later but, because the disease is closely related to dengue and yellow fever, false positives and false negatives may occur, especially in areas where those diseases circulate. More complex “neutralization assay testing” can lower the false-positive rate, but not eliminate it.
9.
I’m pregnant and live in or recently visited a country with Zika virus. What do I do?
Pregnant women should get blood tests and ultrasound scans.
According to the C.D.C., all pregnant women who have visited areas with Zika transmission should be tested, whether or not they have symptoms.
All pregnant women who live in those areas, such as Puerto Rico or American Samoa, should be tested at least twice during their pregnancies, whether or not they have symptoms.
All pregnant women who test positive or had symptoms should have a series of ultrasounds looking for evidence of fetal microcephaly or calcifications, small white spots indicating cell death or inflammation in the brain.
Brain damage has been detected as early as week 19 of a pregnancy — about midway through the second trimester. But it is not clear how quickly damage becomes detectable after an infection.
10.
I’m of childbearing age, but not pregnant and not planning to get pregnant. Should I go to an affected country?
Only if you use birth control consistently.
Half of pregnancies are unintended, according to some surveys. If you want to visit a country where Zika transmission has been reported, Dr. Laura E. Riley, a specialist in high-risk pregnancies at Massachusetts General Hospital, advises strict use of birth control.
Women who become unexpectedly pregnant while traveling or shortly afterward will have to deal with blood tests, regular ultrasounds and a great deal of anxiety.
“Why would you ever sign yourself up for that?” Dr. Riley said. “There’s enough in life to worry about. I wouldn’t add that to my list.”
11.
I’m pregnant now, but wasn’t when I visited one of the affected countries. What’s the risk?
Virtually nil.
Women who recover from the infection are believed to immune to it, so no harm can come to a new baby.
To be sure no virus is in the blood even after a silent infection, the C.D.C. recommends waiting eight weeks — triple the amount of time the virus has been known to persist — before trying to conceive.
Whether that immunity is lifelong is not yet known, because the virus has only been studied carefully for a brief time. But it is believed to be long-lasting.
“Our understanding thus far is that the risk is very, very low if you were in that place prior to conception,” Dr. Riley, of Massachusetts General Hospital, said.
“I wouldn’t be worried about if you conceived after you got back to the U.S.”
12.
If I live in an area where the virus is circulating, should I delay becoming pregnant?
That may be wise, some officials say.
Health officials in several countries, including Brazil, Colombia, Ecuador, El Salvador and Jamaica — and in the territory of Puerto Rico — have suggested that women delay pregnancy temporarily. Obstetricians in some countries are privately giving patients the same advice, saying the risk of fetal damage during an epidemic’s peak is too great.
Once “herd immunity” is strong because many people have been bitten and have recovered, local epidemics may fade out, so that women can safely become pregnant again. Also, many companies are working on Zika vaccines, and delaying pregnancy will buy time for them to arrive.
Gleyse Kelly da Silva holding her daughter, Maria Giovanna, who was born with microcephaly in Recife, Brazil. The birth defect has been linked to the Zika virus.
Credit
Felipe Dana/Associated Press
13.
Does it matter when in her pregnancy a woman is infected with the Zika virus?
Anytime during pregnancy may be dangerous.
Originally, doctors in Brazil believed that infections in the first trimester were the most dangerous, because mothers who gave birth to babies with microcephaly were usually infected then.
A later study found that some mothers infected late in pregnancy also had disastrous outcomes, including the sudden deaths of infants in the womb.
Some experts who have studied the long-term consequences of rubella — another virus that attacks fetuses — say they believe that children who survive a Zika infection without microcephaly nonetheless may suffer serious consequences, including blindness and deafness at birth, learning and behavior difficulties in childhood, and perhaps even mental disabilities later in life.
14.
Should infants be tested?
Other birth defects may be linked to the virus.
Federal health officials say that newborns should be tested for infection with the Zika virus if their mothers have visited or lived in any country experiencing an outbreak and if the mothers’ own tests are positive or inconclusive.
The reason, officials said, is that infection with the virus could be linked to defects in vision and hearing, among other abnormalities, even if the child does not suffer microcephaly.
15.
I’m a man and have returned from a place where the Zika virus is spreading. How long until I can be sure that I won’t infect a sexual partner?
Err on the side of caution.
Whether or not you have had symptoms, you should do everything you can to avoid infecting a woman who may be pregnant or is trying to become pregnant, because the consequences for the baby may be disastrous.
To do that, you must avoid vaginal, anal and oral sex for the length of the pregnancy — or use condoms every time.
It is not known how long the Zika virus remains infectious in semen, but viral RNA has been found in semen more than two months after symptoms subsided. The testes are somewhat shielded from the immune system, so it may take longer for the body to eliminate an infection there.
The C.D.C. recommends that men who have traveled to Zika-infected areas, but had no symptoms, wait eight weeks before having unprotected sex.
Men who have had a positive Zika test or any symptoms of infection, on the other hand, should wait six months.
And in one case in France, a man who never reported symptoms is believed to have infected his wife through sex.
16.
Is there a treatment?
No.
The C.D.C. does not recommend a particular antiviral medication for people infected with the Zika virus. The symptoms are mild – when they appear at all – and usually require only rest, nourishment and other supportive care.
Health workers sprayed insecticide in the Sambadrome in Rio de Janeiro as part of a campaign to combat mosquitoes, which transmit the Zika virus.
17.
Is there a vaccine? How should people protect themselves?
Protection is difficult in mosquito-infested regions.
There is no vaccine against the Zika virus. Efforts to make one have just begun, and creating and testing a vaccine normally takes years and costs hundreds of millions of dollars.
Because it is impossible to completely prevent mosquito bites, the C.D.C. has advised pregnant women to avoid going to regions where the virus is being transmitted, and has advised women thinking of becoming pregnant to consult doctors before going.
Travelers to these countries are advised to avoid or minimize mosquito bites by staying in screened or air-conditioned rooms or sleeping under mosquito nets; wearing insect repellent at all times; and wearing long pants, long sleeves, shoes and hats.
How Zika Spread Around the World
How Zika Spread
Around the World
Pakistan
Nigeria
Before 2007
Costa Rica
Uganda
Indonesia
2007-2014
Yap (Micronesia)
Thailand
Gabon
French Polynesia
Easter Island
2015-2016
Mexico
Cape
Verde
Brazil
Maldives
Fiji
How Zika Spread
Around the World
Pakistan
Nigeria
Before 2007
Costa Rica
Uganda
Indonesia
2007-2014
Thailand
Yap (Micronesia)
Gabon
Easter Island
2015-2016
Cape
Verde
Mexico
Fiji
Brazil
Maldives
How Zika Spread
Around the World
Before 2007
Uganda
2007-2014
Gabon
Yap (Micronesia)
2015-2016
Brazil
Fiji
Maldives
By Jasmine Lee | Source: World Health Organization
18.
If the Zika virus has been in Africa and Asia for decades, why wasn’t a link to microcephaly detected earlier?
It may be that the virus had never struck such a large population without immunity.
Microcephaly is rare, and it has many other causes, including infection of the fetus with rubella (German measles), cytomegalovirus or toxoplasmosis; poisoning of the fetus by alcohol, mercury or radiation; or severe maternal malnutrition and diabetes. It is also caused by several gene mutations, including Down syndrome.
Until recently, health officials paid little attention to the Zika virus. It circulated in the same regions as dengue and chikungunya, and compared with those two painful infections – nicknamed “break-bone fever” and “bending-up fever” – Zika was usually mild.
The virus is thought to have reached Asia from Africa at least 50 years ago. While it may have caused spikes in microcephaly as it first spread, there was no testing to pin down which of many possible causes was to blame.
In 2007, a Southeast Asian strain of the Zika virus began leapfrogging the South Pacific, sparking rapid outbreaks on islands where no one had immunity to it. Because island populations are small, rare side effects did not occur often enough to be noticed. But in 2013, during an outbreak in French Polynesia, which has 270,000 residents, doctors confirmed 42 cases of Guillain-Barrê syndrome, which can cause paralysis. That was about eight times the normal number and the first hint that the Zika virus can attack the nervous system, which includes the brain.
Zika was first confirmed in Brazil – a country of 200 million – last May, and it spread rapidly. The first alarms about microcephaly were raised in October, when doctors in the northeastern state of Pernambuco reported a surge in babies born with it. Pernambuco has nine million people and 129,000 annual births. In a typical year, nine are microcephalic infants.
By November 2015, when Brazil declared a health emergency, Pernambuco had had 646 such births.
19.
Has a Zika outbreak outside Brazil ever been linked to microcephaly?
Officials in French Polynesia have suspicions about an outbreak two years ago.
French Polynesia is the only area outside Brazil to be affected by a Zika outbreak in which public health officials have identified an increase in the number of fetuses and babies with unusually small heads. There is “very high suspicion” of a link between the Zika virus and microcephaly in French Polynesia, said Dr. Didier Musso, an infectious disease specialist at the archipelago’s Institut Louis Malardé – though he said additional research was needed.
In November, French Polynesian officials took another look at an outbreak of the Zika virus that lasted from October 2013 to April 2014. They reported finding an unusual increase – from around one case annually to 17 cases in 2014-15 – of unborn babies developing “central nervous system malformations,” a classification that includes microcephaly.
There were no investigations at the time to determine whether the mothers were infected with the Zika virus during pregnancy. Four of the mothers were tested later, and the results indicated they may have been infected. Additional research is underway, Dr. Musso said.