As we've discussed previously, community acquired pneumonia (CAP) is the #1 cause of hospitalization of adults with an infectious disease in the United States, and yet, in more than half of the cases the type of infection (viral, fungal, bacterial) is never actually identified.
A 2015 study published in the NEJM (see The CDC’s EPIC CA-Pneumonia Study) followed 2500 cases over 5 years and found that in the majority (62%) of cases no definitive pathogenic agent was identified.Among those that were identified – viral infections out-numbered bacterial infections by roughly 2:1.
Specifically, they found:Even without a definitive diagnosis, patients can be treated empirically. But CAP (etiology either known or unknown) inflicts a significant burden in terms of morbidity and mortality.
The most commonly detected pathogens were:
- one or more viruses in 530 (23%) cases
- bacteria in 247 (11%) cases
- bacterial and viral pathogens in 59 (3%) cases
- and a fungal or mycobacterial pathogen in 17 (1%) of cases
- Human rhinovirus (in 9% of patients)
- Influenza virus (in 6%)
- and Streptococcus pneumoniae (in 5%).
When a cluster of atypical pneumonia cases is identified - in a neighborhood, or linked to a specific event, or location - an epidemiological investigation is usually mounted by public health officials.
Over the years we've looked at many, including:
Today we have such a report, on the UK' PHE investigation of a cluster of (what was eventually determined to be) Psittacosis among office workers without obvious exposure to birds.Psittacosis - often called parrot fever - is a relatively rare, atypical bacterial pneumonia caused by Chlamydia psittaci. Large outbreaks are uncommon, but we've seen some small clusters of cases around the world over the past decade.
I've reproduced the abstract below, but you'll want to follow the link to read the full report on the challenges faced by these investigators. When you return, I'll have a bit more on Psittacosis, and how it once caused a panic in the United States.
A Psittacosis Outbreak among English Office Workers with Little or No Contact with Birds, August 2015
April 27, 2018 ·
John Mair-Jenkins, Tracey Lamming, Andy Dziadosz, Daniel Flecknoe, Thomas Stubington, Massimo Mentasti, Peter Muir, Philip Monk
AbstractWhile the exact source of infection was not identified by these researchers, the the available evidence pointed more to a shared environmental exposure than to human-to-human transmission.
Introduction: On 14th August 2015 an office manager informed Public Health England of five employees known to have been diagnosed with pneumonia over the previous three weeks. We investigated to establish whether an outbreak occurred and to identify and control the source of infection.
Methods: We undertook case finding for self-reported pneumonia cases at local businesses (July-August 2015). Clinical samples from a hospitalised case were tested for common respiratory pathogens, but returned negative results. Further testing confirmed Chlamydia psittaci infection in this case (serology and PCR). We subsequently undertook C. psittaci testing for all cases, redefining them as confirmed (C. psittaci PCR or high antibody titre via serology) or probable (inconclusive C. psittaci serology). Twenty-eight day exposure histories informed descriptive epidemiological analysis. We conducted an environmental investigation at the office to identify potential sources of exposure.
Results: We identified six office workers with pneumonia; four met case definitions (three confirmed, one probable) with symptom onset between 29th July and 4th August 2015. Workplace was the only epidemiological link and only one case reported limited, indirect bird contact. Environmental investigations identified pigeons roosting near the office which were being fed by workers (none cases).
Discussion: This was a probable outbreak of psittacosis with no direct bird-to-human contact reported. Cases recovered after receiving appropriate antibiotics. Feeding of pigeons was stopped. A deep clean of office ventilation systems was conducted and workers were advised to avoid bird contact. We hypothesised that indirect environmental exposure to infected pigeons was to the source of this outbreak. This work provides evidence that health professionals should consider psittacosis in the differential diagnosis of cases of severe or atypical respiratory illness even without overt bird contact.
Human infection, at least until relatively recently, has been solely attributed to direct or indirect contact with infected birds.But in 2012, the journal Eurosurveillance carried a report called Psittacosis outbreak in Tayside, Scotland, December 2011 to February 2012, involving four family members and a health-care worker, which suggested human-to-human transmission.
The following year, in Sweden Reports Rare Outbreak Of Parrot Fever, we saw a credible report of human transmission of parrot fever, where a 75 year old man who died in Kronoberg appeared to have spread the infection to at least 8 close contacts, including healthcare personnel.
In 2014, the ECDC's Eurosurveillance Journal carried a follow up report called:
Eurosurveillance, Volume 19, Issue 42, 23 October 2014Surveillance and outbreak reports
Multiple human-to-human transmission from a severe case of psittacosis, Sweden, January–February 2013
Proven transmission of Chlamydia psittaci between humans has been described on only one occasion previously. We describe an outbreak which occurred in Sweden in early 2013, where the epidemiological and serological investigation suggests that one patient, severely ill with psittacosis after exposure to wild bird droppings, transmitted the disease to ten others: Two family members, one hospital roommate and seven hospital caregivers. Three cases also provided respiratory samples that could be analysed by PCR. All the obtained C. psittaci sequences were indistinguishable and clustered within genotype A.
The finding has implications for the management of severely ill patients with atypical pneumonia, because these patients may be more contagious than was previously thought. In order to prevent nosocomial person-to-person transmission of C. psittaci, stricter hygiene measures may need to be applied.While H-2-H transmission of C. psittaci now appears possible, contact with birds still appears to be the primary route of transmission (by far).
Six years ago, in How Parrot Fever Changed Public Health In America, we looked at the fascinating (and tragic) story of how a multi-state outbreak of parrot fever in 1929 - 10 years after the end to the Great Pandemic - sparked a brief national panic, and led to the deaths of several of the public health officials investigating the mysterious epidemic.Before it was quashed, the outbreak sparked 169 cases of parrot fever nationwide, along with 33 deaths (including Dr. Daniel S. Hatfield and Dr. William Stokes of the Baltimore Health Department, and Henry (Shorty) Anderson of the Hygienic Lab).
But out of this tragedy also came congressional funding for a new, far better equipped national public health laboratory.One that today you know as the National Institute of Health.