LIVING THE LAB LIFE
A BLOG FOR ASCLS REGION V
I came across an interesting news article the other day. Global health correspondent for BBC News, Tulip Mazumdar, discussed three viruses that have been labelled as the next potential agent for global healthcare crisis. We are all aware of the destruction caused by Ebola and Zika, for which no vaccine was developed. Having vaccines developed at the onset of outbreaks can keep the illness from spreading and evolving into full-fledged epidemics. Right now, a coalition of charities and governments has committed $460 million to developing these vaccines, while researchers are seeking another $500 million from the funders and the World Economic Forum Davos. This money will be used to develop two vaccines for each of the three viruses, to be made available within five years.
The three viruses Mazumdar discussed in “Vaccines for three deadly viruses fast-tracked” where the MERS virus, Lassa virus, and Nipah virus. In the following review, I will discuss what we already know about these viruses.
Middle eastern respiratory syndrome (MERS) virus comes from the Coronavirus family, the same family as the severe acute respiratory syndrome (SARS) virus. Coronaviruses are plus-strand RNA viruses that cause upper respiratory tract infections in humans. Most of these infections are harmless colds (Coronaviruses are second only to Rhinoviruses in causing common colds). Both MERS and SARS cause a much more severe respiratory infection. Before SARS, only two coronavirus strains had been isolated in humans, but the family has been a subject of much research since SARS first appeared in 2003.
Since September of 2012 (when the MERS virus was first identified in Saudi Arabia), the World Health Organization has been notified of 1,879 laboratory-confirmed cases of MERS in twenty-seven countries, with 666 deaths (mortality rate of 35%). Camels have been indicated as a natural reservoir host for MERS virus, with both camel to human and direct human to human modes of transmission contributing to human infections.
Lassa virus belongs to the family Arenaviruses, which are enveloped single-stranded RNA viruses. This is a hemorrhagic fever virus, like it more famous friend the Filovirus Ebola. Lassa virus made quite an entrance back in 1969. The virus’ first victims where two nurses who worked at a mission in Lassa, Nigeria. A third nurse was saved when she was airlifted to Yale University Medical School in New Haven, CT. Researchers at Yale successfully isolated the new virus from their patient, but at a cost: one virologist became ill and survived, and one laboratory technician died after being infected. The virologist’s survival was attributed to transfusion with plasma from the Lassa-infected nurse that had survived.
Even though Lassa virus first came on the scene in 1969, little is known about how the virus works because its area of activity includes the countries of Sierra Leone, Liberia, and Guinea, which have seen years of civil war and unrest, to the deterrence of research activities. Cultural factors have also inhibited research: in certain African cultures, the manipulation of a body after death is taboo, therefore autopsies are off-limits. The natural reservoir for Lassa is the West African mouse Mastomys natalensis, which then can spread the virus by entering human homes and sheading the virus through their urine. Human to human transmission is possible, but is far less common. Most infections occur after contact with infected mouse urine.
Lassa is believed to be endemic in many West African countries, with only 20% of those infected showing any clinical presentation. Estimates put the annual death toll for Lassa at about 5,000.
Nipah virus belongs to the family of Paramyxoviruses, which also includes several famous viruses: the measles virus, the mumps virus, parainfluenza virus, respiratory syncytial virus, and human metapneumovirus. Paramyxoviruses are non-segmented minus-strand RNA viruses. Nipah virus was first discovered in Malaysia in 1998 after an outbreak of severe encephalitis that killed over one-hundred people (108 deceased out of 269 known cases, approximately 40% mortality rate). This virus first infected pigs, and then spread on to the human host. After the initial outbreak, one million pigs were slaughtered to prevent the spread of the disease; this mass-slaughtering did succeed in curtailing the outbreak. The pteropid bat appears to be the natural host for this virus as well as other members of the Paramyxovirus family, the Hendra and Menangle viruses. Bats spread the virus to the pigs (that show few clinical symptoms), the pigs then spread the virus both to each other and to humans who worked with them. There were no identified cases of human to human transmission in this outbreak. In later outbreaks occurring in Bangladesh in 2004, pigs did not serve as the intermediate hosts, so it is not clear if the virus spread from bat to human or if some human to human transmission occurred. Additionally, it is worth noting that the outbreaks in Bangladesh saw a mortality rate of 74%--yikes!
It is important to note that human activity is likely responsible for the initial outbreak of this virus. A large area of rainforest was cleared to make room for a new airport at Kuala Lumpur. The bats that had been living in this rainforest then re-habituated to areas surrounding local pig farms. This same destruction of habitats of host animals contributed to the spread of the Ebola virus through West Africa.
In the outbreaks where they have been indicated, these viruses have caused substantial morbidity and mortality. We cannot afford to wait until an epidemic starts to start developing a vaccine that would have prevented infection in the first place. If any good can come from serious epidemics like Ebola and Zika, let it be that more time and money is invested into vaccine development before epidemics occur.
Mazumdar, T. (2017, January 18). Vaccines for three deadly viruses fast-tracked. BBC News. Retrieved January 20, 2017, from http://www.bbc.com/news
Norkin, L. C. (2010). Virology: Molecular Biology and Pathogenesis. Washington, DC: ASM Press.
World Health Organization. (2016, December 5). Middle East respiratory syndrome coronavirus (MERS-CoV). Retrieved January 22, 2017, from http://www.who.int/