UH OH
Ebola virus in survivors can trigger outbreaks years after infection
Guinea began a new round of Ebola vaccinations this year after an outbreak of the virus that research found stemmed from a survivor
CAROL VALADE AFP/File
Issued on: 15/09/2021 -
Tokyo (AFP)
Ebola survivors can relapse and trigger outbreaks at least five years after infection, and long-term follow-up of former patients is needed to prevent devastating flare-ups, according to new research.
Scientists already knew Ebola could lie dormant in survivors, who test negative because the virus is in tissue rather than circulating in the blood.
But analysis of an outbreak this year in Guinea, published Wednesday in the journal Nature, found these "virus reservoirs" can awaken and cause new infections and transmission years on.
To trace the source of the Guinea outbreak, which involved 16 confirmed cases, 12 of whom died, researchers analysed the genomes of samples from several patients.
Ebola outbreaks are usually thought to result from the virus "spilling" from an animal host to a human.
But the analysis showed the Guinea strain was virtually identical to that from a 2013-16 wave.
If the virus had been circulating actively in the community since then, it would have accumulated a certain number of mutations as it spread.
Instead, the 2021 virus had just 12 changes, "far fewer than would be expected... during six years of sustained human-to-human transmission".
That strongly suggests the source was reactivated virus that had lain dormant in a survivor, said Alpha Keita, a researcher at the University of Montpellier who led the study.
"This is the longest known time between the declared end of an epidemic and a viral resurgence," he told AFP.
"It's a new paradigm: the possibility that transmission from an individual infected during a previous epidemic could be the source of a new outbreak."
How and why dormant Ebola virus suddenly awakens and sickens a person remains something of a mystery, though there are some tantalising clues.
Sometimes a spike in Ebola antibodies can be detected in survivors at a given time -- a possible sign that the body is responding to a resurgent virus.
Around two-thirds of Ebola survivors have high antibody levels even five years after infection, but "the question to pose is what happens if there's a resurgence in the people whose immunity has dropped", said Keita.
- Fears of stigma -
The study's findings have "considerable implications for public health and care of survivors of Ebola", said Robert F. Garry of Tulane University's School of Medicine.
"Humans can now be added to the list of intermediate hosts that can serve as long-term Ebola virus 'reservoirs' and trigger new outbreaks," he wrote in a review commissioned by Nature.
He sees the need to prioritise healthcare workers for vaccination and monitor Ebola survivors for signs of a flare-up.
And Keita wants a rethink of the term "Ebola survivor" to include not only those who battled through symptoms but also those who may have been infected without becoming ill.
Even asymptomatic individuals "could be the starting point" for an outbreak, he warned.
"We need a real, long-term follow-up protocol for former Ebola patients and their contacts so we can catch resurgence in previously infected people in time."
He cautions though that follow-up must be done cautiously to avoid ostracisation of survivors, a point echoed by Trudie Lang, director of Oxford University's Global Health Network.
"These people are considered heroes by some for surviving," she said.
"Yet (they) could also be stigmatised and excluded if there is a fear of these individuals presenting a risk."
Lang, who was not involved in the study, called it "important new evidence," and a reminder of the need to support research on threats other than Covid-19.
Keita said the research paves the way for various additional study, including on what causes viral resurgence and the possibility of eradicating Ebola reservoirs in survivors.
© 2021 AFP
Ebola: Profile of a dreaded killer
Issued on: 15/09/2021 -
Tokyo (AFP)
Ebola survivors can relapse and trigger outbreaks at least five years after infection, and long-term follow-up of former patients is needed to prevent devastating flare-ups, according to new research.
Scientists already knew Ebola could lie dormant in survivors, who test negative because the virus is in tissue rather than circulating in the blood.
But analysis of an outbreak this year in Guinea, published Wednesday in the journal Nature, found these "virus reservoirs" can awaken and cause new infections and transmission years on.
To trace the source of the Guinea outbreak, which involved 16 confirmed cases, 12 of whom died, researchers analysed the genomes of samples from several patients.
Ebola outbreaks are usually thought to result from the virus "spilling" from an animal host to a human.
But the analysis showed the Guinea strain was virtually identical to that from a 2013-16 wave.
If the virus had been circulating actively in the community since then, it would have accumulated a certain number of mutations as it spread.
Instead, the 2021 virus had just 12 changes, "far fewer than would be expected... during six years of sustained human-to-human transmission".
That strongly suggests the source was reactivated virus that had lain dormant in a survivor, said Alpha Keita, a researcher at the University of Montpellier who led the study.
"This is the longest known time between the declared end of an epidemic and a viral resurgence," he told AFP.
"It's a new paradigm: the possibility that transmission from an individual infected during a previous epidemic could be the source of a new outbreak."
How and why dormant Ebola virus suddenly awakens and sickens a person remains something of a mystery, though there are some tantalising clues.
Sometimes a spike in Ebola antibodies can be detected in survivors at a given time -- a possible sign that the body is responding to a resurgent virus.
Around two-thirds of Ebola survivors have high antibody levels even five years after infection, but "the question to pose is what happens if there's a resurgence in the people whose immunity has dropped", said Keita.
- Fears of stigma -
The study's findings have "considerable implications for public health and care of survivors of Ebola", said Robert F. Garry of Tulane University's School of Medicine.
"Humans can now be added to the list of intermediate hosts that can serve as long-term Ebola virus 'reservoirs' and trigger new outbreaks," he wrote in a review commissioned by Nature.
He sees the need to prioritise healthcare workers for vaccination and monitor Ebola survivors for signs of a flare-up.
And Keita wants a rethink of the term "Ebola survivor" to include not only those who battled through symptoms but also those who may have been infected without becoming ill.
Even asymptomatic individuals "could be the starting point" for an outbreak, he warned.
"We need a real, long-term follow-up protocol for former Ebola patients and their contacts so we can catch resurgence in previously infected people in time."
He cautions though that follow-up must be done cautiously to avoid ostracisation of survivors, a point echoed by Trudie Lang, director of Oxford University's Global Health Network.
"These people are considered heroes by some for surviving," she said.
"Yet (they) could also be stigmatised and excluded if there is a fear of these individuals presenting a risk."
Lang, who was not involved in the study, called it "important new evidence," and a reminder of the need to support research on threats other than Covid-19.
Keita said the research paves the way for various additional study, including on what causes viral resurgence and the possibility of eradicating Ebola reservoirs in survivors.
© 2021 AFP
Ebola: Profile of a dreaded killer
Detection by mutation John SAEKI AFP
Issued on: 15/09/2021 - 17:24
Paris (AFP)
Ebola, which could reappear years later in survivors according to a study published by the journal Nature on Wednesday, has killed more than 15,000 people since 1976.
Here is a factfile on the widely feared disease:
- Origins -
Ebola is a viral haemorrhagic fever that was first identified in central Africa in 1976. The disease was named after a river in the Democratic Republic of Congo, then known as Zaire.
Five of the virus species are known to cause disease in humans -- Zaire, Sudan, Bundibugyo, Reston and Tai Forest.
The first three have resulted in serious outbreaks in Africa.
- Transmission -
The virus' natural reservoir animal is suspected to be a species of fruit bat, which does not itself fall ill but can pass the disease on to primates, including humans. Humans become exposed to the virus if they kill or butcher infected bats for food.
Among humans, the virus is passed on by contact with the blood, body fluids, secretions or organs of an infected or recently deceased person. This can include touching a sick or dead person, and likely also sexual intercourse.
Those infected do not become contagious until symptoms appear. They become more and more contagious until just after their death, which poses great risks during funerals.
Death rates are high, at around 50 percent on average of those infected, and up to 90 percent for some epidemics, World Health Organization (WHO) data show.
According to the study published Wednesday, it is possible that Ebola remains dormant in survivors before reappearing several years later and potentially causing a new outbreak.
- Symptoms -
Following an incubation period of between two and 21 days, Ebola develops into a high fever, weakness, intense muscle and joint pain, headaches and a sore throat.
The initial symptoms are often followed by vomiting and diarrhoea, skin eruptions, kidney and liver failure, and sometimes internal and external bleeding.
- Treatment -
A vaccine developed by the US group Merck Sharp and Dohme was found to be very effective in a major study carried out in Guinea in 2015.
It was pre-qualified by the WHO and more than 300,000 doses have been used during a vaccination programme in the DR Congo.
A second experimental vaccine developed by the US group Johnson & Johnson was introduced preventively in October 2019 in areas that had not been affected by the virus, and more than 20,000 people were inoculated.
- Worst epidemic (2013-2016) -
The worst-ever Ebola outbreak began in December 2013 in southern Guinea before spreading to two neighbouring West African countries, Liberia and Sierra Leone.
That outbreak killed more than 11,300 people out of nearly 29,000 registered cases, according to WHO estimates.
- 10th and 11th DR Congo epidemics -
The 10th epidemic began in August 2018 in the North Kivu province of DR Congo. The WHO declared it a global health threat in July 2019.
DR Congo authorities declared it over in June the following year after around 2,280 people had died, making it Africa's second-worst Ebola outbreak.
That month in the Equateur province, an 11th Ebola epidemic began and it was declared over in November, with 55 deaths.
- DR Congo, Guinea -
The DR Congo said in February 2021 that a resurgence of the virus had been identified in an eastern part of the country.
Vaccines were rolled out and the 12th epidemic was declared over in May, at a cost of six lives.
Guinea also reported an "epidemic situation" in its southeast in February. After the rapid use of vaccines, the official end of the second epidemic was declared in June after 12 deaths.
- Ivory Coast: False alarm -
On August 14, Ivory Coast announced its first known case of the disease since 1994, in an 18-year-old Guinean woman recently arrived in Abidjan.
But after new studies by the Institut Pasteur in France, the WHO announced at the end of August that the patient had not had the disease and there was "no evidence" of Ebola in the country.
© 2021 AFP
Issued on: 15/09/2021 - 17:24
Paris (AFP)
Ebola, which could reappear years later in survivors according to a study published by the journal Nature on Wednesday, has killed more than 15,000 people since 1976.
Here is a factfile on the widely feared disease:
- Origins -
Ebola is a viral haemorrhagic fever that was first identified in central Africa in 1976. The disease was named after a river in the Democratic Republic of Congo, then known as Zaire.
Five of the virus species are known to cause disease in humans -- Zaire, Sudan, Bundibugyo, Reston and Tai Forest.
The first three have resulted in serious outbreaks in Africa.
- Transmission -
The virus' natural reservoir animal is suspected to be a species of fruit bat, which does not itself fall ill but can pass the disease on to primates, including humans. Humans become exposed to the virus if they kill or butcher infected bats for food.
Among humans, the virus is passed on by contact with the blood, body fluids, secretions or organs of an infected or recently deceased person. This can include touching a sick or dead person, and likely also sexual intercourse.
Those infected do not become contagious until symptoms appear. They become more and more contagious until just after their death, which poses great risks during funerals.
Death rates are high, at around 50 percent on average of those infected, and up to 90 percent for some epidemics, World Health Organization (WHO) data show.
According to the study published Wednesday, it is possible that Ebola remains dormant in survivors before reappearing several years later and potentially causing a new outbreak.
- Symptoms -
Following an incubation period of between two and 21 days, Ebola develops into a high fever, weakness, intense muscle and joint pain, headaches and a sore throat.
The initial symptoms are often followed by vomiting and diarrhoea, skin eruptions, kidney and liver failure, and sometimes internal and external bleeding.
- Treatment -
A vaccine developed by the US group Merck Sharp and Dohme was found to be very effective in a major study carried out in Guinea in 2015.
It was pre-qualified by the WHO and more than 300,000 doses have been used during a vaccination programme in the DR Congo.
A second experimental vaccine developed by the US group Johnson & Johnson was introduced preventively in October 2019 in areas that had not been affected by the virus, and more than 20,000 people were inoculated.
- Worst epidemic (2013-2016) -
The worst-ever Ebola outbreak began in December 2013 in southern Guinea before spreading to two neighbouring West African countries, Liberia and Sierra Leone.
That outbreak killed more than 11,300 people out of nearly 29,000 registered cases, according to WHO estimates.
- 10th and 11th DR Congo epidemics -
The 10th epidemic began in August 2018 in the North Kivu province of DR Congo. The WHO declared it a global health threat in July 2019.
DR Congo authorities declared it over in June the following year after around 2,280 people had died, making it Africa's second-worst Ebola outbreak.
That month in the Equateur province, an 11th Ebola epidemic began and it was declared over in November, with 55 deaths.
- DR Congo, Guinea -
The DR Congo said in February 2021 that a resurgence of the virus had been identified in an eastern part of the country.
Vaccines were rolled out and the 12th epidemic was declared over in May, at a cost of six lives.
Guinea also reported an "epidemic situation" in its southeast in February. After the rapid use of vaccines, the official end of the second epidemic was declared in June after 12 deaths.
- Ivory Coast: False alarm -
On August 14, Ivory Coast announced its first known case of the disease since 1994, in an 18-year-old Guinean woman recently arrived in Abidjan.
But after new studies by the Institut Pasteur in France, the WHO announced at the end of August that the patient had not had the disease and there was "no evidence" of Ebola in the country.
© 2021 AFP
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