New Delhi: The dreaded Ebola virus disease outbreak in West Africa may officially be over but there’s a new threat on the horizon.

A little-known virus called Zika is sending waves of panic in South America after being identified as the possible cause of infants being born with abnormally small heads.

Zika fever is spread by several species of Aedes mosquitoes, including Aedes aegypti, the mosquito that spreads dengue fever.

The virus usually causes fever, rash, headaches, joint and muscle pain as well as a non-purulent conjunctivitis, but some patients are also asymptomatic.

In November and December, the Pan-American Health Organization (PAHO) of the World Health Organization (WHO), warned about a large number of cases of congenital birth defects, and especially a birth defect known as microcephaly, which is a condition associated with incomplete brain development.

On Thursday, WHO announced that the Ebola virus disease outbreak in Liberia and West Africa that claimed the lives of more than 11,300 people and infected over 28,500 was over. It, however, did not rule out the occasional flare-up.

Liberia was first declared free of Ebola transmission in May 2015, but the virus re-emerged twice after that, the last time in November. This is the first time since the start of the epidemic two years ago that all three of the hardest-hit countries—Guinea, Liberia and Sierra Leone—have reported zero cases for at least 42 days. Sierra Leone was declared free of Ebola transmission on 7 November 2015 and Guinea on 29 December.

Evidence shows that the virus disappears relatively quickly from survivors, but can remain in the semen of a small number of male survivors for as long as one year, and in rare instances, be transmitted to intimate partners.

The WHO cautioned that the three countries remain at high risk of small outbreaks of Ubola, such as the most recent one in Liberia.

The Zika threat was discussed in an editorial in peer-reviewed scientific journal PLOS Neglected Tropical Diseases earlier this week by co-editors-in-chief Peter J. Hotez and Serap Aksoy.

PAHO’s 1 December alert reported 1,248 cases of microcephaly in Brazil, a 20-fold increase compared to previous years. The highest rates of Zika-caused microcephaly are currently in Brazil.

The causal link between Zika and microcephaly has still not been established, but there is some preliminary evidence of the link. According to PAHO, the Brazilian ministry of health and scientists showed that the Zika virus’s genomic DNA was present in the blood and tissues of a baby with microcephaly, and that the virus was also detected in two pregnant women whose foetuses were diagnosed through ultrasonography with microcephaly.

According to reports, health officials in Brazil have even warned women against getting pregnant due to the spread of the virus.

Hotes and Aksoy concluded that Zika will join a growing list of neglected tropical diseases that disproportionately affect female reproductive health.