By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

SYNOPSIS: Chronic Q fever is a frequent and potentially lethal complication of acute infection that may first be diagnosed a decade afterward.

SOURCE: Buijs SB, Bleeker-Rovers CP, van Roeden SE, et al. Still new chronic Q fever cases diagnosed eight years after a large Q fever outbreak. Clin Infect Dis 2021; May 24:ciab476. doi: 10.1093/cid/ciab476. [Online ahead of print].

During 2007-2010, an outbreak of acute Q fever originating in dairy goat farms affected approximately 4,000 people in the Netherlands. In some regions, as many as 15% of the local population were infected.1 Buijs and colleagues have examined the frequency and timing of subsequent chronic Q fever in a retrospective examination of 519 cases diagnosed at 45 participating hospitals. Of these, the diagnosis was proven in 313 (60.3%), probable in 61 (51.6%), and possible in 124 (24.1%). The mean age was 64.5 years, and three-fourths were male.

A focus of infection was identified in the majority, with a vascular (aneurysm or vascular prosthesis) source in 192 cases (37.0%), endocarditis in 192 (37.0%), and a combination of vascular source and endocarditis in 52 (10.0%). No focus was identified in 156 cases (30.1%), most of whom had only a possible diagnosis. Antibiotic therapy was initiated in 290 (92.7%) proven chronic Q fever patients, 54 (66.7%) probable chronic Q fever patients, and 20 (16.0%) possible chronic Q fever patients. Of the 519 cases, 160 (30.8%) previously had serologically diagnosed acute infection, 143 (89.4%) of whom received antibiotic therapy, but only three-fourths of these received a regimen judged to be likely effective. The median interval between the occurrence of acute Q fever and the diagnosis of chronic infection was 13.0 months (interquartile range [IQR], 8.0-22.0). The longest observed interval in a patient whose acute infection was proven was 8.5 years, and it was 9.2 years in a patient with a history consistent with acute Q fever but without serological confirmation at the time.

Among the 200 patients in whom the date of onset of acute Q fever was known, the diagnosis of chronic Q fever was made after an interval of more than two years in 45 (22.5%). In this group, the median interval to diagnosis was 42.0 months (IQR, 32.0-52.0). Of those for whom the interval was known, 40 (20%) developed complications of chronic Q fever and these occurred more frequently in those whose interval to diagnosis was more than two years.

The complications attributed to chronic Q fever included vascular aneurysm in 96 cases (25.4%), abscess formation in 86 cases (22.8%), and heart failure in 82 cases (21.7%). Death that was definitely or probably related to chronic Q fever occurred in 83 (26.5%) patients with proven chronic infection as well as in three (3.7%) with possible chronic Q fever. The median interval from diagnosis to a related death was 10 (IQR, 1.0-26.0) months. The most frequent cause of death was attributed to an “acute aneurysm,” which accounted for 29 (33.7%) of the total deaths.

COMMENTARY

In the spring of 1996, 230 goats were removed from a ranch and placed in a Humane Society facility in San Mateo, CA.2 Many of the goats were pregnant, and 39 kids were born. Some days later, a staff veterinarian became ill with a temperature of
103.5° F, and this was followed by similar illness in others with exposure to the animals, including visitors seeking to adopt pet dogs and cats. I saw some of those affected in my practice, including a young woman who had been assigned to deal with the goats who became ill, as did her partner, who had been exposed to a kid that she had brought home to care for since it seemed to be ill and let it sleep with them.

After seeing a number of patients with acute Q fever related to the outbreak, I visited the Humane Society facility and subsequently spoke with the state public health officer about further investigation and follow-up of affected individuals with monitoring for complications. However, this suggestion was rejected — consistent with their public statements: “Health officials said yesterday that they have already tested some 300 people and expect to be queried by as many as 500, but they reassured people throughout the Bay Area that the illness is no worse than a routine case of flu and is marked by the same symptoms. ... [They] explained the nature of Q fever to the Peninsula shelter’s entire staff to reassure them that they were in no danger of significant disease ... [and] reassured the public that the blood test is simple, the disease disappears quickly.”2

Contrast that approach with the statement of Buijs and colleagues, who continued to recognize an average of 20 newly diagnosed cases of Q fever each year in their cohort: “We urge physicians to remain vigilant for chronic Q fever for many years after a large outbreak and in patients previously diagnosed with acute Q fever and perform microbiological testing at the vaguest hint of symptoms.” 

REFERENCES

  1. van der Hoek W, Morroy G, Renders NH, et al. Epidemic Q fever in humans in the Netherlands. Adv Exp Med Biol 2012;984:329-364.
  2. Perlman D. Q fever no worse than flu, experts say. Sept. 21, 1996. https://www.sfgate.com/bayarea/article/Q-Fever-No-Worse-Than-Flu-Experts-Say-2965464.php?utm_campaign=CMS%20Sharing%20Tools%20(Premium)&utm_source=share-by-email&utm_medium=email