A QUANTUM OF SCIENCE
Emergent viral outbreaks show Ebola is not the only "hot zone" virus worth fearing
Sub-Saharan Africa has long been known as the Hot Zone, a place from which some of the world’s most deadly viruses originated. Among them are the well-known Ebola and Marburg viruses, members of the viral hemorrhagic fever (VHF) family that cause extreme fever, internal and external bleeding and rapid death among a frighteningly high percentage of those infected. Other "Old World" (i.e. African) hemorrhagic viral diseases include dengue and yellow fever. Most VHF viruses are carried by rodents – which seem largely immune – and are spread to humans by liquid contact, though some are capable of aerosol infections. (This latter category includes the Marburg virus, which was weaponized by the former Soviet Union in the 1980’s.) Less well-known cousins in this same family are the so-called New World viruses such as hantavirus, as well as the Argentine, Bolivian, and Venezuelan hemorrhagic fevers.
Late last fall an African travel agent was flown from the city of Lusaka to Johannesburg, South Africa, suffering from high fever and external bleeding. She died a few days later. Within the next several days, the paramedic who received her into the hospital, a nurse who cleaned the room following the travel agent’s death, and a nurse who attended the paramedic after he became ill, all perished from the same virus. Another nurse who treated the paramedic was given an antiviral treatment and survived. This was the beginning and end – for now – of an outbreak of the Lujo Virus, named for the two cities where it was first observed (Lusaka and Johannesburg). A member of the VHF family, it has more in common with the New World branch than it does Ebola or Marburg. Genetic analysis by researchers at Columbia University showed that the Lujo virus was a member of the arenaviridae genus (the name comes from the Latin word for sand, referring to the way viral particles of this genus appear when viewed under a microscope). Strangely, arenaviruses are almost unknown in Africa but have several species native to South America. Comparing the genetic sequence of Lujo to other VHF species from Africa showed significant differences, strongly suggesting that Lujo was not a simple mutant or even a more virulent strain caused by reassortment of viral chromosomes (such as is often the case for the influenza virus). Instead, Lujo appears to be the first high-morbidity, high-mortality VHF virus to emerge from Africa’s hot zone in the last thirty years.
In 2006 a paper was published by Dr. C.J. Peters, a member of the University of Texas Medical Branch, discussing the factors that affect the accelerating rate of emergence of new viruses and increasingly deadly outbreaks. He referenced the Emerging Microbial Threats reports issued by the Institute of Medicine in 1992 and updated in 2002, in which all the data pointed to two major factors at play in the increasing danger of deadly microbial outbreaks: multiple ecologic niches and ever-accelerating human travel and transport. In this paper he describes an arenavirus outbreak in a small village in Bolivia in 1962. The village suffered an outbreak of "black typhus" and out of 600 villager there were 107 cases, of which more than four out of ten perished. This is roughly the same morbidity and mortality rates recorded for the medieval scourge of bubonic plague, better known as the Black Death.
Since the 1960's, large sections of the Amazonian plateau have been deforested, and human activity in those regions has reached levels never before seen. The same is true of sub-Saharan Africa, where the Lujo virus emerged in 2008; had the Lujo virus not been caught before it spread thanks to current medical expertise not available in 1962, the "black typhus" outbreak may well have paled in comparison to the devastation Lujo might have wrought.
The story of ecological niches created through human activity has become hauntingly familiar, and authorities predict that the problem will only worsen as population pressures push humans deeper into the hot zones of viral reservoirs in both the Old World and the New.
For more information:
Viral hemorrhagic fever (overview)
Googleblog article on early news of the Lujo outbreak
News article on Columbia researcher’s efforts to analyze Lujo
Genetic Detection and Characterization of Lujo Virus, a New Hemorrhagic Fever–Associated Arenavirus from Southern Africa (Lipkin et al).
NOVA interview discussing Soviet weaponization of Marburg virus
© A Quantum of Science / P. Smalley
Reproduction with attribution is appreciation
Showing posts with label mortality. Show all posts
Showing posts with label mortality. Show all posts
Thursday, July 9, 2009
Wednesday, May 20, 2009
Mapping H1N1
A QUANTUM OF SCIENCE
Where in the world is H1N1?
The spread of H1N1 around the world has significant implications for the etiology and epidemiology of the disease, as well as the global health infrastructure’s response to it. Raw numbers alone do not tell the story as well as this single image, taken from the WHO pandemic alert and response website.
This map is current: as of today there are a global total of 10,243 laboratory-confirmed cases of H1N1 influenza that have been reported to the WHO, including 80 deaths (making the global mortality rate one death out of every 128 cases). While the actual number of total cases is inevitably somewhat higher due to the lagging nature of lab confirmations and reporting, what is more interesting is the distribution of the cases – and deaths – and what this might tell us about the past and future of H1N1.
Originally dubbed as Swine Flu, the official name for this strain of H1N1 is North American influenza, and indeed the overwhelming majority of the cases are in North America (93.8%). What is interesting to note is that 79 of the 80 confirmed deaths are also in North America (98.75%). Digging a little deeper into the distribution of deaths, we find that this is due to the large contribution of deaths from H1N1 in Mexico, where the mortality rate is one death for every 50.6 cases. That is two and a half times the global mortality rate, and eighteen times the mortality rate in the adjacent United States. With the sequencing of the H1N1 genome in Canada that was announced yesterday, no significant differences were found in strains isolated in Mexico versus those in the United States or Canada. While this is somewhat reassuring because it means there is not a more virulent strain on the loose in Mexico, it requires a different explanation. Some authorities have suggested Mexico has deficiencies in its health infrastructure, but others cite a cultural inhibition that may play a more pervasive role in preventing infected persons from seeking help until it is too late. In either case, however, countries with similar health infrastructures and cultures would be expected to have a similar mortality rate, and this has not yet been borne out (as the map’s number for Central and South America show).
Another point of interest brought out by the map of H1N1 cases to date are the non-North American hot spots. Japan is the leader of these, with 210 cases, followed almost evenly by Spain (107) and the United Kingdom (102). What is interesting about this is the far-flung locations of the hotspots outside North America. Nothing like the close distribution of cases in Mexico-US-Canada have been seen in these Asian and European hotspots. This could mean that there is something particular to North America that supports the infectivity of the viral strain; or it could mean that it is simply too soon, and the neighbors of these hotspots will soon show a commensurate rise in cases. It is worth noting that strains of influenza are known to show a strong geographical preference; the deadly Bird flu (H5N1) is almost unknown outside of the Far East, for reasons that scientists are still trying to elucidate. This also brings up the potential for reassortment of viral genes between H1N1 and H5N1, now that the former has entered the latter’s territory. Still, Japan has been aggressive about treating flu cases and currently Roche (the maker of Tamiflu) estimates that 35 million of the 50 million people who have been treated with Tamiflu are in Japan. It can be hoped that this aggressive treatment schedule will be effective in containing the possible hybridization of H1N1 with H5N1.
For more information:
WHO Epidemic and Pandemic Alert and Response
WHO H1N1 map (20-May-2009 version)
Tamiflu (Oseltamivir) information, including use in Japan
© A Quantum of Science / Peter Smalley (2009)
Reproduction with attribution is appreciation
Where in the world is H1N1?
The spread of H1N1 around the world has significant implications for the etiology and epidemiology of the disease, as well as the global health infrastructure’s response to it. Raw numbers alone do not tell the story as well as this single image, taken from the WHO pandemic alert and response website.
This map is current: as of today there are a global total of 10,243 laboratory-confirmed cases of H1N1 influenza that have been reported to the WHO, including 80 deaths (making the global mortality rate one death out of every 128 cases). While the actual number of total cases is inevitably somewhat higher due to the lagging nature of lab confirmations and reporting, what is more interesting is the distribution of the cases – and deaths – and what this might tell us about the past and future of H1N1.
Originally dubbed as Swine Flu, the official name for this strain of H1N1 is North American influenza, and indeed the overwhelming majority of the cases are in North America (93.8%). What is interesting to note is that 79 of the 80 confirmed deaths are also in North America (98.75%). Digging a little deeper into the distribution of deaths, we find that this is due to the large contribution of deaths from H1N1 in Mexico, where the mortality rate is one death for every 50.6 cases. That is two and a half times the global mortality rate, and eighteen times the mortality rate in the adjacent United States. With the sequencing of the H1N1 genome in Canada that was announced yesterday, no significant differences were found in strains isolated in Mexico versus those in the United States or Canada. While this is somewhat reassuring because it means there is not a more virulent strain on the loose in Mexico, it requires a different explanation. Some authorities have suggested Mexico has deficiencies in its health infrastructure, but others cite a cultural inhibition that may play a more pervasive role in preventing infected persons from seeking help until it is too late. In either case, however, countries with similar health infrastructures and cultures would be expected to have a similar mortality rate, and this has not yet been borne out (as the map’s number for Central and South America show).
Another point of interest brought out by the map of H1N1 cases to date are the non-North American hot spots. Japan is the leader of these, with 210 cases, followed almost evenly by Spain (107) and the United Kingdom (102). What is interesting about this is the far-flung locations of the hotspots outside North America. Nothing like the close distribution of cases in Mexico-US-Canada have been seen in these Asian and European hotspots. This could mean that there is something particular to North America that supports the infectivity of the viral strain; or it could mean that it is simply too soon, and the neighbors of these hotspots will soon show a commensurate rise in cases. It is worth noting that strains of influenza are known to show a strong geographical preference; the deadly Bird flu (H5N1) is almost unknown outside of the Far East, for reasons that scientists are still trying to elucidate. This also brings up the potential for reassortment of viral genes between H1N1 and H5N1, now that the former has entered the latter’s territory. Still, Japan has been aggressive about treating flu cases and currently Roche (the maker of Tamiflu) estimates that 35 million of the 50 million people who have been treated with Tamiflu are in Japan. It can be hoped that this aggressive treatment schedule will be effective in containing the possible hybridization of H1N1 with H5N1.
For more information:
WHO Epidemic and Pandemic Alert and Response
WHO H1N1 map (20-May-2009 version)
Tamiflu (Oseltamivir) information, including use in Japan
© A Quantum of Science / Peter Smalley (2009)
Reproduction with attribution is appreciation
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