Better understanding the home care environment

While hospital acquired infections (HAIs) threaten the wellbeing of many patients, those who are immunocompromised or immunosuppressed, such as hematopoietic stem cell transplant (HSCT) recipients, are at particular risk. Such patients are vulnerable to infections from other people (e.g., visitors, other patients, HCWs), the environment (e.g., surfaces, unfiltered air, linens), and themselves (e.g., pathogens shed from their own GI tract).

Infection is a significant cause of mortality in this population in the months following transplant and considerable care is taken to protect patients in the hospital. When they are well enough, recipients are released to go home and receive care there, with periodic visits to clinic. Typically, they and their home care providers are trained on how to prevent infections (e.g., through appropriate central venous line care, wearing of masks, etc), and sometimes home care nurses visit to ensure appropriate care is delivered. Medical supplies (infusion pumps, line care kits, saline, heparin, etc) are delivered; the house becomes a mini-hospital for care of the patient.

The approach seems to work well from an infection prevention perspective, but it's hard to be sure given the paucity of studies in the literature on the incidence of infections in home care populations. If the home care environment is protective to the patient, it's important to understand why that is, and if it's a threat, it's important to know that as well. Understanding the risk of infection in this patient population at home versus in highly controlled environments is important.

On the one hand, there's a different infection pressure in the home relative to a hospital. Presumably it's decreased at home, as there are no surrounding patients and there are fewer contacts with HCWs per unit of time. On the other hand, there is risk from contact with their home care providers, who often interact with many other people outside the home daily.

Moreover, the microbial environment of the home, as it relates to hematology/oncology patient health, doesn't seem to be as well characterized as that of the hospital environment. Looking through the literature that does exist isn't entirely reassuring. Whereas in bone marrow transplant (and related) wards there is extensive guidance on air filtration, cleaning procedures, and protocols for visitors, the analogous issues (e.g., ventilation, dust, cleaning) in homes are much more variable. The presence of pets may add additional risk. Furthermore, recovering patients often travel to and from hospital clinics on a daily or weekly basis. The automobile can also be a mode for infection, as has been pointed out recently for Legionella.

Improved surveillance for home care infections could lead to a better knowledge of the epidemiology of these infections and potentially identification of modifiable risk factors. 

(image source: Wikipedia)

A fictional story: Counterpoint and extension

Today we welcome our first guest blogger, Dave Bridgelend, a mathematical modeler who focuses on business modeling and simulation. Dave has created business models for government agencies, financial services companies, telecommunications companies, energy companies, and healthcare organizations. He is the co-author of the book "Business modeling: A practical guide to realizing business value".

David Hartley recently described an attempt to reduce hospital acquired infections at the (fictional) Generic General Hospital. The attempt seemed successful, until the hospital CEO considered the broader impact of the effort. The budget for routine HAI prevention activities was raided to fund the improvement, and that budget diversion would likely cause unintended consequences.

But there is a bit more to this story. After the GGH CEO lectured her staff on unintended consequences, the GGH patient advocate spoke up. She pointed out that GGH already scored well on the HCAHPS measures of hospital acquired infections, earning ratings of "Better than the US national benchmark" on CAUTI and MRSA, and ratings of "No different form the US national benchmark" on the other four HAI measures.

"And when patients choose a hospital, they look at HAI a bit, but most of their decision is driven by what they hear from their personal networks. Last year when Martha was in the hospital for a week, the hospital made a big stink about her daughter staying in the room with her.  When Joe broke his leg, the hospital was too loud at night for him to sleep. When Carol had her hip replaced, she said the bathroom was dirty."

She continued: "I understand we want to improve GGH. But let's focus our attention on what the patients care about. Further reducing HAI won't bring them here. Keeping the bathrooms clean will."

(image source: Wikipedia)

Legionella on ice

"Legionnaires' disease" was the name originally given to an illness observed at a 1976 American Legion convention. Today, we call the illness associated with Legionella pneumophila infection, which can range from mild respiratory illness to severe pneumonia, "legionellosis". Legionella bacteria exist naturally in water and moist soil and colonies tend to grow in warm water, pools of which often form in improperly operated or maintained HVAC systems, hot tubs, and hot water systems. Legionella is an important cause of both hospital- and community-acquired pneumonia in both immunocompetent and immunosuppressed patients. Hospital-acquired cases are often associated with potable water systems colonised with Legionella.

A story in the Pittsburgh Tribune-Review recently described an unusual outbreak at a Pittsburgh hospital. Although the epidemiology showed an association with ice chips, investigators were unable to find Legionella in the hospital water system. How could Legionella appear in ice from machines supplied by cold (not hot) water lines free from the bacterium? It was ultimately determined reservoirs within hospital ice machines were warmed by internal compressors, thus allowing Legionella colonies to grow.

Previous outbreaks involving ice makers and Legionella have been described in the literature (see, e.g., Schuetz et al, 2009, Graman et al, 1997, and Stout et al, 1985), but I doubt that many would immediately respond "ice machine" when asked about likely sources of Legionella infection in a hospital. Though anecdotal, this story illustrates how counter-intuitive outbreak investigation can be: One wouldn't necessarily think to look in a freezer for a bug that needs warm water to grow. But there it was, and hospital investigators figured it out when the ice chips were implicated. Bravo! 

(image source: Wikipedia)

Semmelweis and hand hygiene

Dr Ignaz Semmelweis was a Hungarian born physician who worked in Vienna in the 1840s. He is popularly credited with the discovery of the importance of handwashing, though perhaps it's more accurate to say that he was among the first to appreciate the importance of hand hygiene, rather than handwashing.  Harbarth (2000) points out that

. . . many scientists have cited Semmelweis' observations, but, amazingly, grossly misleading impressions still arise about Semmelweis and his original idea of antiseptic hand disinfection, often wrongly cited as “handwashing” in the English-language literature. In fact, Semmelweis never promoted handwashing with soap and water; he was opposed to it, since he wrote: “The cadaveric particles clinging to the hands are not entirely removed by the ordinary method of washing the hands with soap.… For that reason, the hands of the examiner must be cleansed with chlorine, not only after handling cadavers, but likewise after examining patients”

Indeed, Semmelweis promoted a policy of using a solution of chlorinated lime (calcium hypochlorite) on the hands between autopsy work and the examination of patients, as opposed to soap.

So, let's celebrate Semmelweis' insights about the importance of the hands in infection prevention rather than associating his name with handwashing alone. He's recently come back on Twitter to help us -- and certainly we need that help. The WHO's World Hand Hygiene Day is May 5. Check out how you can help raise awareness about hand hygiene.

(image source: WHO)

First US MERS case announced

Yesterday the first case of Middle East respiratory syndrome (MERS) observed in the US was announced. The case is a man who flew to Chicago, Illinois from Riyadh, Saudi Arabia by way of London, England. After landing in Chicago, he took a bus to Indiana. He arrived in the US on April 24 and began experiencing shortness of breath, coughing, and fever on April 27. He presented to a community hospital in Munster, Indiana, on April 28; because of his symptoms and travel history, the man was tested for the MERS coronavirus.

Understandably, the story is being covered widely in the press. One can learn more about MERS from several sources. The ECDC MERS-CoV epidemiological update as of April 30 is an excellent summary of MERS globally, and additional resources can be found at the CDC MERS Website. UPMC has also published a nice summary of the global situation. 

It would be interesting to utilize mathematical modeling to estimate where, assuming the patient was infectious while on the bus and planes, new cases might be likely to develop, geographically speaking. Such analysis could be helpful for instituting intensified surveillance in the places most likely to have such cases; using models, it may be possible to forecast the most likely cities. A rich set of methods, spanning the 1960s to the present, has been developed to understand the spatio-temporal spread of influenza and those could probably be adapted for such purposes if data on domestic bus, rail, and air travel since the plane landed is available. And while it's true that significant uncertainties in latency and incubation periods, transmission rates, and other epidemiologic parameters exist, there are techniques that allow us to estimate the effects of such uncertainties on model results.

Gathering the data, especially the transportation data, may be difficult. A NYT article this morning noted

The typical incubation period for MERS is five days, and the patient is not known to have infected anyone else. Airline passenger lists will be used to contact everyone who sat near him.

But because bus companies often do not know who bought tickets or who sat where, “that bus ride may be a challenge,” said Tom Skinner, a C.D.C. spokesman.

Information on rail passengers may be similarly difficult.

The time to develop adaptable modeling capabilities and gather such data is before new diseases emerge and spread. Of course, it's not possible to anticipate specific details about a new disease prior to emergence, but we do have some data on MERS already, plus lots of insight into how respiratory diseases spread in general. 

Regardless of models, it will be interesting to watch the MERS situation develop globally in the coming months.

(image source: CDC)