May 16, 1995

Article at Canberra Times

FEATURE | Cocktail of new viruses emerges


Health workers in protective gear begin their shift at an Ebola treatment centre in Beni, Democratic Republic of Congo

Ebola is not the only bug worrying scientists, says WILSON da SILVA

ANXIOUS SCIENTISTS in protective bubble suits. A doomsday virus spreading rapidly, its victims bleeding through the eyes while their organs turn to mush.

It may sound like the plot of the Dustin Hoffman film Outbreak, but it is happening today in Zaire. Ebola, the deadly virus upon which the film is based, has returned in an epidemic proportion after 16 years.

But the worst of it is, Ebola isn’t the only nasty new bug worrying scientists. There has been a cocktail of so-called “emerging viruses” in the past few years, each with varying degrees of deadliness. The best-known is HIV, but others have been springing up.

Last year, Australian scientists came across Equine morbillivirus, a previously unknown organism that appeared without warning, killed 14 horses in Queensland within days and sent two men to hospital. One of them, trainer Vic Rail, eventually died a wheezing, ghastly death.

“No-one can work out where the viruses go between outbreaks, and no-one’s found the reservoir,” says senior scientist Margery Kennett, of Melbourne’s Fairfield Hospital, which houses one of the country’s high-security “hot labs” for handling highly infectious diseases.

“It appears and disappears, and no-one knows exactly how it’s transmitted. One ‘index’ case suddenly appears, and he’s bleeding like mad and all of a sudden, there’s another 10 and it grows exponentially after that.”

The outbreak which began in Kikwit, population 500,000, has already killed 59 people and the toll is expected to rise. Zairean authorities have quarantined the city and ordered the province sealed off from the capital Kinshasa, 500km away and with a population of five million.

Medical teams from the World Health Organisation, the Centres for Disease Control in the United States, the Pasteur Institute in France and the National Institute for Virology in South Africa are converging on the area to try to prevent Ebola’s spread.

Of the emerging viruses which have infected humans, Ebola is the most feared. It is classed as a “Biohazard Level 4”, the highest level of risk and, were it to spread widely, could slaughter perhaps hundreds of millions around the world, researchers say. Known to have caused outbreaks only twice since it was identified in 1976, it was also the subject of a bestselling book, The Hot Zone.

At first, the virus triggers nausea and discomfort. This is followed by fever, bleeding gums and vomiting of blood. Inside the body, the disease begins to break down the tissue walls of organs, and these haemorrhage profusely. Six days later, victims are dead, their insides liquefied, their organs disintegrated.

“The only thing you can do is try to contain it.” says Professor Frank Fenner, a renowned virologist at the ANU’s John Curtin School of Medical Research. “There’s no vaccine, no drug that has the slightest effect on it.”

At its last two known epidemic appearances, in 1976 and 1979, the Ebola virus killed hundreds in Zaire and then Sudan before it was successfully contained. It then disappeared. Another outbreak took place at an American research facility in Reston, Virginia, in 1989, when an infected monkey imported from the Philippines for experimentation infected others, and scores of the creatures died. A number of lab workers also became ill. Luckily, this strain of the virus — although it looked exactly the same as the African version under the microscope — was not lethal to humans.

Ebola is a filovirus, or “thread-shaped” virus, of a type which has only been seen by scientists once before. The first was discovered in 1967 when laboratory staff in Marburg, Germany, fell violently ill after handling a shipment of African green monkeys from Uganda. Dubbed the “Marburg virus”, this first recorded outbreak sent 31 people to hospital, of which seven died. Only three cases since have been definitively blamed on the Marburg virus.

ANOTHER concern to medical authorities is the emerging Arena virus family, of which Lassa and Hantaviruses are two of most dangerous. The first recorded outbreak of Hanta has been traced back to the Korean War, when more than 2000 United Nations soldiers contracted the disease, and many died. The virus, which is now known to reside inside field mice inhabiting an ecological niche near the Demilitarised Zone, was later carried aboard ships to the United States where, in 1993, it caused an outbreak that infected 72 American Indians in the south-west. All developed haemorrhagic fever similar to that caused by Ebola, and more than half died.

The virus then went underground. Since being identified by modern genetic analysis techniques, virulent outbreaks have been recognised in Greece and the Balkans, and a much milder form has been found in Scandinavia, large areas of the former Soviet Union, and in various scattered parts of Europe. In South Korea, 13 per cent of rats tested in Seoul carried antibodies to the virus, and a global study has since found antibodies in rats in North and South America, Australia, Asia and Europe. A related cousin of the virus has been found in 80 per cent of adult rats tested in Baltimore.

A health worker in a biocontainment suit holding infected child in the Democratic Republic of the Congo

Although there have been no known Hanta outbreaks in the east coast of the US, some scientists speculate that the virus may be partly responsible for the high level of kidney disease among inner-city residents of Baltimore. One per cent of kidney dialysis patients at one Baltimore hospital tested positive for Hantaviruses antibodies.

Australia has also spawned its own deadly emerging virus last year. On September 21 in Hendra, near Brisbane, 21 racehorses at the stables of trainer Vic Rail fell ill, running up temperatures of 41 degrees. They had difficulty breathing and were spluttering a bloody froth from their mouths and noses. Fourteen died within

48 hours of presenting the symptoms, and Mr Rail and his stable hand also came down with a respiratory illness.

Scientists at the CSIRO’s Australian Animal Health Laboratory in Geelong, an imposing concrete bunker that is one of the world’s most advanced infectious-disease centres, worked around the clock to find the cause. Mr Rail died during the search, raising the stakes and confirming the researchers’ worst fears — this was a completely new bug that could “jump” to humans. A panic was triggered in the horse industry across the country, and races were cancelled.

Seven days after the outbreak was reported, the Geelong scientists identified a deadly new virus, and developed a testing method to detect it. Over the following few months, more than 2500 horse samples and 150 human samples were tested, but the virus was not found. Although it appears to have disappeared, researchers warn that it is a dangerous new disease, capable of killing rapidly.

“Once it’s in your body, it’s extremely virulent. Really virulent,” says Dr Allan Gould, a molecular biologist at the Geelong facility whose genetic sequencing of the bug pinned down the culprit as a completely new virus. “The thing that stopped this from being a major catastrophe is the fact that it’s not very contagious.”

But Gould, along with other scientists interviewed, warned that these viruses are extremely unpredictable. Ebola, Marburg, Hanta, Lassa and the Australian Equine morbillivirus are all RNA viruses — viruses which mutate rapidly because they lack a “proofreading” ability during replication.

Each outbreak can represent a different strain, perhaps more deadly or more contagious than its predecessor. A virulent Ebola-like virus, if transmissible via airborne particles like the Reston strain but (unlike the Reston strain) was also lethal to humans, could rapidly grow into a global epidemic. HIV, also classed as an emerging virus, was one genie that could not be put back in the bottle once it escaped. 

ALREADY, ANTIBODIES to variants of Ebola have been detected in monkeys arriving in Western laboratories from Indonesia and the Philippines, and tests in the Philippines have found antibodies in monkey handlers working for researchers and in the bloodstream of villagers and macaques on Mindanao.

Shortly after the resumption in 1990 of monkey shipments to the Reston laboratory — site of the only recorded US outbreak of Ebola in 1989 — more than 80 per cent of the animals developed Ebola within months of arrival. The infection became so widespread, reaching other unconnected rooms, that all of the laboratory’s animals had to be sacrificed.

Scientists do not know the link between the Ebola variants in Asian monkeys and the prevalence of Ebola in Africa or where the virus resides between out-breaks. The Reston outbreak suggests the Asian variants may not be fatal to humans: no-one knows for sure.