In Ibura, a poor neighbourhood in Recife, north eastern Brazil, Gleyse Kelly, 27, breastfeeds her three-month-old daughter, Giovanna.
"I hope that she will be able to walk, talk and go on to study," Gleyse says.
Giovanna has microcephaly, a condition which causes babies to be born with smaller-than-average heads and suffer varying degrees of brain damage, leading to developmental problems and severe learning difficulties. Some die shortly after birth.
Experts say it is very likely that Giovanna will require full-time care for the rest of her life, putting enormous pressure on Gleyse, a mother of four who earns only $250 a month working as a toll booth attendant, and who receives $25 in government child benefits. Her husband is unemployed.
The World Health Organization has called a global state of emergency over the mosquito-borne zika virus and a rise in the number of babies born with microcephaly that is suspected to be related to it. So far, more than 1.5 million cases of zika have been detected in Brazil, with the overwhelming majority of cases in the poorer north eastern states of Pernambuco, Bahia and Paraiba.
Zika and microcephaly: what we don't know
The true scale of the crisis remains unknown, however, as the link between zika and microcephaly, while strongly suspected, remains scientifically unproven. So far, only a handful of microcephaly cases have a proven connection to zika.
Experts say a lack of knowledge about zika is the greatest challenge to tackling the virus. Part of the problem is the complexity and cost of the diagnostics, as the virus usually lives in the body for only a week. The virus' symptoms are minimal - mostly rashes and mild fever - and usually go unnoticed.
While more than 4,000 suspected cases of microcephaly were originally reported, these numbers are now being scrutinised and, to date, only 270 cases have been confirmed. In 2014, there were just 150 cases.
The condition can also be caused by alcohol abuse, malnutrition and diabetes, as well as by other infectious diseases.
Annually, there are around 25,000 cases of microcephaly reported in the United States, leading analysts to question whether the number of cases in Brazil was previously under-reported or whether the supposed surge is a result of over awareness following increased media exposure.
|Giovanna is three months old and likely to need full-time care for the rest of her life [Sam Cowie/Al Jazeera]
Authorities are unanimous, however, in saying that much remains unknown, and pregnant women especially should err on the side of caution.
"The zika virus is very serious. This is the biggest public health threat we have faced in recent history," said Jalison Correia, the secretary of public health for the city of Recife.
Correia added that Brazil's current economic recession is posing a challenge, but said no costs would be spared in tackling the virus. According to Correia, the city asked for R$29B ($7.46m) in emergency funding from the federal government and received just R$1.3B ($334,000).
The World Health Organization has advised pregnant women against travelling to Brazil and for women living in zika-affected areas to seek professional advice.
|Experts say that a lack of knowledge about zika is the greatest challenge to tackling the virus [Sam Cowie/Al Jazeera]
While implementing measures to tackle the virus, authorities have downplayed suggestions that it will affect Brazil's Olympic and Paralympic Games, to be held in Rio de Janeiro during Brazil's winter, when the conditions mean there are fewer of the aedes aegypti mosquitoes, which spread zika, dengue and chikungunya, to breed.
The zika virus has also reignited Brazil's abortion debate. Activists are calling for the Supreme Court to loosen the country's extremely restrictive abortion laws - which permit it only in the case of rape and if the woman's life is in danger - for those carrying microcephaly-affected babies.
Attacking the transmitter
Addressing the nation, Brazil's president, Dilma Rouseff, called on people to help the government fight the virus.
"The most effective way is not letting the mosquito be born, destroying their breeding sites, of which more than two thirds are in our homes," Rouseff said. Currently, there is no cure for zika and a vaccine is expected to take years to develop.
On February 13, after Brazil's annual carnival, 220,000 troops will be deployed across 28 states of Brazil to visit houses and destroy mosquito breeding sites. In Recife and the north-eastern states troops have been mobilising for weeks.
|Brazil's President Dilma Rouseff called on the nation to engage with the government to fight the virus [Sam Cowie/Al Jazeera]
In Coqueiro, a poor neighbourhood in Recife, troops go door to door and health workers give out leaflets to residents advising them on how to avoid mosquito-borne viruses.
The soldiers find mosquito larvae, formed in rainwater and collected in a tyre that a resident had left outside his house for six months. When questioned about why he left it there during the rainy season, he said: "I forgot."
At one house, a middle-aged woman says that everyone in her family has suffered from dengue fever, which is also transmitted by mosquitoes. Health workers advise her that the paddling pool in her back yard will breed larvae if not emptied soon.
Poverty as an exacerbating factor
While experts say that the main reason for the spread of zika cases in the northeast is probably because that was the virus's entry point, poverty is clearly an exacerbating factor.
GDP per capita in 2013 for the state of Pernambuco was R$15,282 ($3,900), with Bahia at R$13,578 ($3,490) and Paraíba at just R$11,835 ($3,044), compared with R$39,122 ($10,063) in Sao Paulo.
While social and economic indicators have improved significantly over the past 10 years, the northeast region still has the country's worst access to healthcare and education as well as sanitation and running water.
READ MORE: What is the zika virus?
The region is also arid and historically drought-stricken, meaning that locals are more likely to keep water supplies at home in tanks, which can create mosquito breeding grounds if only minimally damaged.
Poor neighbourhoods also suffer from bad infrastructure. They are often informally built and end up collecting pockets of rainwater during the rainy season. Rubbish disposal is badly organised and collection often sporadic.
"This isn't a condition that just affects poor people. A mosquito can bite anyone. But the condition clearly favours poverty," said Angela Rocha, at the Oswaldo Cruz hospital in Recife, where the zika outbreak was first recorded.
Back at Gleyse Kelly's house, her mother, husband and three sons sit in the living room. Gleyse answers messages on her mobile phone while cradling baby Giovanna. She smiles and kisses her daughter's head.
"My biggest fear when I was pregnant was that she would die after I gave birth," she said
|Gleyse Kelly says she feared her daughter would die shortly after birth [Sam Cowie/Al Jazeera]
Source: Al Jazeera