THE EBOLA VIRUS may have reemerged in a woman a year after she survived contracting the deadly virus.

The woman’s husband and two of their sons may have been infected with the virus as a result.

Researchers looking into the last-known cluster of infections from a source within Liberia, occurring in November 2015, said the case highlights the need for continued surveillance.

In a research paper published in The Lancet Infectious Diseases journal, they said transmissions from latent Ebola virus infections are rare, but that their findings highlight the importance of close surveillance once countries are declared Ebola-free.

The virus can persist in certain parts of the body after recovery from acute infection, and Ebola virus RNA has previously been detected in semen, breast milk and cerebrospinal fluid (which is found in the brain and spinal cord) of survivors.

Previously there have only been two cases of the virus reemerging, and this new cluster is the first indication of transmission from a persistently infected female survivor of Ebola virus disease.

“Despite no current active Ebola virus transmission chains in west Africa, Ebola virus persistence could pose a continued risk for resurgence of cases and may have the potential for a large-scale outbreak, if not detected rapidly and controlled,” lead author Emily Kainne Dokubo of the US Centers for Disease Control and Prevention said.

Further studies are needed to better understand viral persistence and transmission, and to reduce stigma against survivors.

“Additionally, countries and global health partners should continue to focus on strengthening health systems to prevent, rapidly detect, and respond to Ebola virus infections in the region,” she stated.

11,000 deaths

In 2014 and 2015, the Ebola virus disease outbreak in west Africa resulted in more than 28,000 cases and 11,000 deaths across Liberia, Guinea and Sierra Leone.

The first case in Liberia was reported in March 2014, and infection then spread rapidly across the country, killing more than 4,800 people. In May 2015, Liberia was declared free of human-to-human Ebola virus transmission.

In June 2015, a month after Liberia had been declared Ebola-free, a flare-up of a cluster of cases highlighted the potential for retransmission, but the rapid and robust response was effective in limiting additional infections, and the country was again declared free of Ebola virus transmission in September 2015.

As part of the new cluster report, the authors conducted an investigation of a family of six (mother, father and four sons aged two months, five years, eight years and 15 years), and analysed the genetics of the Ebola virus detected among some of the individuals.

Health services first identified the family when the 15-year-old son showed symptoms of the Ebola and tested positive in Monrovia, Liberia, on 19 November 2015. Once the Ebola virus infection was confirmed, he was moved into a treatment unit but died on 23 November.

At this point, both the father and the eight-year-old brother also tested positive for Ebola virus RNA, and experienced some symptoms (tiredness, headache and fever) but both recovered.

Pregnancy 

The mother tested negative for Ebola virus RNA. However, she had positive Ebola virus antibodies indicating prior infection, and an investigation suggested she survived an acute Ebola virus infection in July 2014.

The researchers believe that the mother’s infection may have re-emerged after her pregnancy, making the infection flare-up in October 2015, then transmitting the virus to her family.

Genetic analysis suggests that the virus carried by the father, the 15-year-old son and the eight-year-old son were similar, and that it was a continuation of the 2014 west African Ebola virus outbreak, when the mother suffered an acute infection after having cared for her brother who died from the disease.

The two-month-old son also had a low level of antibodies to the virus, which is likely to be caused by the transfer of maternal antibodies through breast milk.

By assessing the family’s history, the researchers ruled out travel to areas with active Ebola virus transmission, association with people who had travelled from these areas, and contact with animals that could transmit the Ebola virus as the possible source of infection.

Exactly how the virus was passed from family member to family member remains unclear, but the authors suggest it could be close physical contact or contact with bodily fluids.

The authors note some limitations to their study, including that the genetic analysis of the father’s virus in November 2015 was incomplete.

In addition, there were no available samples from the mother and the mother’s brother in 2014. During this time Ebola treatment units had limited capacity to fully investigate and diagnose cases.