MRSA: Closing Schools Just Window Dressing

The key to infectious disease control is striking an appropriate balance between overreaction and underreaction; not quarantining people unjustifiably and not exposing people to risk. This balance can sometimes be hard to find given the penchant of infectious disease to foment panic. However, sometimes it is easy to spot overreaction.

The community college in my hometown is one such example. 

Based on a single case of methicillin resistant Staphylococcus aureus (MRSA) infection the community college shuttered its doors. What strikes me as odd is the presumption that closing the school will have any substantial impact on MRSA at the school. While good sanitation and cleaning is important (and I don't know the particulars of this situation), it will not eliminate the risk of MRSA. The general population harbors MRSA are on the bodies at a rate of around 1% -- that means that the college with an enrollment of over 3800 students has at least 38 students who are chronically colonized with MRSA. Similar rates apply to the faculty and staff. The rate in healthcare workers is, by contrast, about 5% and those with chronic illnesses may have higher rates. Infection occurs primarily through skin-to-skin contact. This single case emerged amongst a larger group of MRSA colonized individuals and not from a school facility or structure.

MRSA is nothing new and no cause for panic. In most people it may cause a minor skin infection or boil (the "spider bite" for which there is no spider). Many people have minor MRSA skin infections that go unnoticed or undiagnosed and resolve on their own. Of course, MRSA can cause more serious infections such as pneumonia, bloodstream infections, infections of heart valves, or infections of bones/joints in certain contexts. 

By scrubbing down the school, a false sense of security will be instilled in the campus community and when the probable next case is announced a new round of panic and demands for more action will arise because the facts about MRSA's presence in the community (it can even be harbored by pets) were not part of the earlier discussion. 

While this may seem like an easy and straight-forward action and a "show of force" amidst the demands to do something, the negative repercussions of non-evidence based actions such as this will likely abound. This action will not substantially protect against or change the risk of infection as it is the campus community itself that harbors the microbe.

The Political Virus-A Review of AIDS: Between Science and Politics by Peter Piot

Infectious disease is, for better or worse, intertwined with politics in a manner no other form of medicine is. While certain infectious disease require core governmental functions such as quarantine to be exercised and bioweapons involve multiple aspects of government role in promoting national security, it goes beyond that -- as a daily perusal of the headlines in our post-Ebola world reveals. Of the infectious diseases, HIV is in a realm all of its own really marking a new phase in how politics and infectious disease interact. While tuberculosis, plague, cholera, yellow fever, and malaria all had political importance, HIV is sui generis. 

I recently finished an excellent, up-to-date guide to the global politics of HIV/AIDS by a major force in the field: AIDS: Between Science and Politics by Dr. Peter Piot, the 1st director of UNAIDS, one of the discoverers of Ebola, and the director of the famed London School of Tropical Medicine and Hygiene. 

The book is based on a series of lecturers Dr. Piot delivered and covers the most pressing aspects of the global battle against HIV/AIDS which is now in its 4th decade. Throughout the book, Dr. Piot concretizes the nuances of the HIV pandemic with special attention to its heterogeneity ("know your epidemic") and the vicissitudes of infection rates, including the alarming increase in cases in American bisexual and homosexual men causing HIV rates in New York City and Washington DC to eclipse rates in some African countries. Dr. Piot also expertly emphasizes that the HIV pandemic is not explained by a simple linear model. For example industrialization can, depending on the context, foster or hinder the spread of HIV. 

Arguing for renewed efforts to harness all the scientific knowledge gleaned--which now includes pathbreaking concepts such as treatment-as-prevention, PrEP, needle exchange, decriminalization of sex work--Piot provides a path forward for controlling what has become the emblematic infectious disease emergency of our time, which killed 1.2 million people in 2014 and approximately 40 million since its jump into our species. 

Inject Drugs, Contract Infection, Repeat

Infectious disease physicians are intimately familiar with injection drug use for the obvious reason that breaching the skin and injecting substances directly into the bloodstream is a path to paradise for most microorganism. Unfortunately for humans, that path to paradise is paved with infective endocarditis (infection of the heart valves), abscesses, infections of veins (septic thrombophlebitis), HIV, hepatitis C, and hepatitis B (not to mention anthrax, tetanus, and botulism). Injection drug use is the primary problem with infections following secondarily and unless the injection drug user stops or is able to learn how to inject more skillfully (with clean needles and skin antisepsis) recurrent infections will be the norm.

This weekend I took care of a thirty-something injection drug user who recently had Staphylococcus aureus ("staph"), a common organism that infects injection drug users, in the bloodstream resulting in destruction of two heart valves as well as an abscess in the aorta. This was treated with a long course of antibiotics followed by surgery that involved the use of prosthetic valves and repair of the aorta. The infection was cured for a while until injection drug use resumed and another bloodstream infection ensued with evidence of infection of all the prosthetic material put in place, a dire situation as bacteria form hardy biofilms on prosthetic material that are somewhat impervious to antibiotic therapy. This will be a difficult infection to control or cure and thoracic surgeons don't relish doing these types of repeat surgeries.

This scenario got me thinking about the phenomenon of injection drug use infections of heart valves and the special problems it poses. Because recurrence is the rule, certain rules applied to valve infections/replacements may not necessarily apply For example, using more durable mechanical heart valves in younger patients and bioprosthetic versions of bovine or pig origin in older patients who will not live long enough for the valve to need replacement. In one study, at 5 years less than half (46.7%) of injection drug users endocarditis patients are alive while over 70% of those that are not injection drug users are alive, arguing against the routine practice of using mechanical valves as a matter of routine in injection drug users. 

I don't know what will happen with this particular patient but the important aspect of the case is understanding that unless the primary problem is corrected -- the injection drug use -- no level of aggressiveness in infection management will ultimately change the outcome.

Touring the World of Infectious Disease: A Review of Sonia Shah's Pandemic

For those who want a grand scale overview of infectious diseases and the big concepts that animate the field, Sonia Shah's Pandemic: Tracking Contagions from Cholera to Ebola, and Beyond is, in my opinion, probably the best book to read.

I read a lot -- and I mean a lot -- of books on infectious disease and Pandemic is exquisite in its approach. Using cholera as the main character to concretize important concepts, Shah expertly weaves in every major outbreak in recent years, from E.coli to Ebola, highlighting important elements that time and again have led to outbreaks, epidemics, and pandemics. For example, one chapter is aptly titled "The logic of pandemics."

Shah's book goes beyond a simple historical account and brings in cutting-edge research, hypotheses, and theories. For example, her discussion of the evolution of sexual reproduction as a resiliency mechanism against microbes is fascinating as is the discussion of the advantages and disadvantages of warm-blooded versus cold-blooded animals.

Shah also provides a great dissection of an oft-repeated myth in infectious disease: that microbes lose virulence over time as they adapt to their host. 

I learned an immense of new information pertaining to infectious disease from this book ranging from the geology of Manhattan (particularly conducive to water contamination) to Martin Luther's penchant for eating feces!

This book has layers and layers of valuable information and I recommend it in the highest possible terms to those interested in taking a tour of this endlessly stimulating field with a extraordinarily insightful guide.

Putting Lipstick on a Pig by Removing PERVs

The New England Journal of Medicine, in its Clinical Implications of Basic Research column, covered a remarkable new study that shows just how revolutionary and pathbreaking the CRISPR-Cas9 gene may be. 

The column -- and the research it is based upon -- integrates across the seemingly disparate field of retrovirology and xenotransplantation. Xenotransplantation is the transplantation of organs from an animal species into humans. Even if a safe and effective technique that minimized organ rejection could be found, however, the problem of xenozoonosis would still exist. 

Xenozoonosis is the transmission of an infectious agent via organ transplantation from one species to another. While screening donor animals for exogenous potential pathogens and raising them in sterile environments may be possible, it is not enough. Endogenous retroviruses integrated into the genomes of animals could activate and infect human cells causing novel zoonotic diseases. The fact that these viruses are literally part of the organism whose organs are being transplanted is a very daunting obstacle to overcome. But not for CRISPR-Cas9. 

CRISPR-Cas9, a revolutionary gene-editing technique that is part of bacteria's immune system, can be used to cut and paste genes in a relatively simple manner. In the study (originally published in Science by Yang along with transplant infectious disease pioneer Jay Fishman and the extremely innovative George Church) detailed in The New England Journal of Medicine, CRISPR-Cas9 was employed successfully to remove porcine endogenous retrovirus (PERV) from pig cell lines. For many reasons, pigs will be the most likely source of organs for humans and PERV is known to have the capacity to infect human cells. 

While this is an early study, its implications are far-reaching -- just imagine the impact on organ transplantation waiting list if pig organs could be safely transplanted into humans.

CRISPR-Cas9 may be the discovery of the millenium.