Ready for deadlier Ebola-like outbreak?
A virus (Marburg) more deadly than Ebola has killed a man in Uganda, confirmed the World Health Organisation on Friday, raising fears of a new outbreak even as the world struggles to contain Ebola, which has killed more than 4,000 people and infected at least twice as many.Updated: Oct 12, 2014 10:52 IST
A virus more deadly than Ebola has killed a man in Uganda, confirmed the World Health Organisation on Friday, raising fears of a new outbreak even as the world struggles to contain Ebola, which has killed more than 4,000 people and infected at least twice as many.
Marburg virus, which is part of the Ebola virus family, killed a 30-year-old radiologist working in Mengo Hospital in Kampala in Uganda last month. At least 146 people who came in contact with him were tracked for symptoms, which are identical to Ebola. Eleven got symptoms but tested negative for Marburg.
Marburg virus, which got its name from the German City of Marburg where the fever was first identified in 1967 among scientists doing laboratory work using African green monkeys (Cercopithecus aethiops) imported from Uganda, is a haemorrhagic fever that causes bleeding, vomiting and diarrhoea, killing up to 90% of those infected. Like Ebola, it spreads through contact with blood, urine, stools or vomit of an infected person, or the body of someone who has died from the disease.
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Since then, sporadic cases and outbreaks have been reported in Angola, Democratic Republic of the Congo (DRC) , Kenya, South Africa (in a person with recent travel history to Zimbabwe) and Uganda, with the last case outbreak of 20 cases and 9 deaths being reported in Uganda in 2012.
Marburg and Ebola viruses are similar but not the same. Bats are the natural hosts for both these viruses from the Filoviridae family (filovirus), which produce clinically similar symptoms which spread quickly in rural communities. Once the outbreak peaks, resource-strapped hospitals have to struggle to hold back staff, who often stay away to look after ill family or friends or simply from fear of getting infected.
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Treating people infected with Ebola is becoming a challenge even in rich countries with adequate medical resources. At Madrid's Carlos III Hospital, for example, where nursing assistant Teresa Romero Ramos died after getting infected while looking after an Ebola-infected missionary, is facing a staff crunch because of infection fears.
Common-sense hygiene can prevent transmission, but fear is rarely rational. Marburg, like Ebola, is not an airborne disease and transmission to stay that way. "At this point in time, we have no evidence and do not anticipate that the Ebola virus is mutating to become airborne," said the UN Mission for Ebola Emergency Response (UNMEER) last week after an intensive fact-finding trip to West Africa.
But unless it's contained quickly, Marburg can spread as rapidly as Ebola virus, which has crossed continents for the first time in 2014.
Since containing Ebola is appearing to be more of a challenge with each passing day, work on vaccines and new treatments has been accelerated. Two candidate vaccines have clinical-grade vials ready for phase 1 clinical trials. One is cAd3-ZEBOV, which uses chimpanzee-derived adenovirus vector with an inserted Ebola virus gene, has been developed by GlaxoSmithKline in collaboration with the US National Institute of Allergy and Infectious Diseases.
The other vaccine is rVSV-ZEBOV, made by the Public Health Agency of Canada by replacing a gene of a weakened (attenuated) vesicular stomatitis virus found in livestock with an Ebola virus gene.
The only tested treatment for Ebola is convalescent therapy, in which an infected person is treated with the antibody-rich blood of a person who has survived the infection. It was first used in 1976 -- the year Ebola was identified in the DRC -- in a woman who was treated with plasma from a person who survived a Marburg virus infection. Though she had less clinical bleeding than the other patients, she died within days. During the 1995 Ebola outbreak in DRC, whole blood from recovered patients was given to eight people. Seven of the eight recovered.
In the current outbreak, convalescent therapy has been used in a few, including two US doctors who became infected in Liberia. Both recovered, but it's difficult to say what worked -- convalescent therapy, the experimental medicines ZMapp used for one and TKM-EBV for the other, or the high-grade supportive care both received in the US, or a combination of all three.
Till a vaccine or cure is found, prevention coupled with realtime surveillance to identify and isolate infected people to stop transmission are what will determine whether Marburg and Ebola outbreaks happen out of Africa.
1 The Ebola virus is transmitted through close and direct physical contact with infected bodily fluids, the most infectious being blood, faeces and vomit.
2 It has been detected in breast milk, urine and semen after recovery, persisting for at least 70 days in semen.
3 Saliva and tears may also carry some risk, with the virus found most frequently in patients at a severe stage of illness.
4 The Ebola virus can be transmitted indirectly, by contact with previously contaminated surfaces and objects, but the risk is low and can be reduced further with cleaning and disinfection.
5 Ebola virus disease is not an airborne infection (inhalation of the virus from a suspended cloud of small dried droplets).
6 Theoretically, wet and bigger droplets from a heavily infected person could transmit the virus – over a short distance – to someone nearby, but there is no evidence of this. Studies from past outbreaks show that all cases were infected by direct close contact with symptomatic patients.
7 Speculation that the Ebola virus might mutate and to spread through air is an a speculation, unsubstantiated by any evidence. There is no evidence that viral diseases change their mode of transmission. For example, the mode of transmission of the H5N1 avian influenza virus, which has caused sporadic human cases since 1997, remains unchanged.
First Published: Oct 11, 2014 17:21 IST