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Volume 26, Number 7—July 2020
CME ACTIVITY - Research

Rickettsioses as Major Etiologies of Unrecognized Acute Febrile Illness, Sabah, East Malaysia

Matthew J. Grigg, Timothy William, Emily G. Clemens, Kaajal Patel, Arjun Chandna, Christopher S. Wilkes, Bridget E. Barber, Nicholas M. Anstey, J. Stephen Dumler, Tsin W. Yeo, and Megan E. RellerComments to Author 
Author affiliations: Infectious Diseases Society Sabah–Menzies School of Health Research, Kota Kinabalu, Malaysia (M.J. Grigg, T. William, K. Patel, A. Chanda, C.S. Wilkes, B.E. Barber, N.M. Anstey, T.W. Yeo); Menzies School of Health Research–Charles Darwin University, Darwin, Northern Territory, Australia (M.J. Grigg, K. Patel, A. Chanda, C.S. Wilkes, B.E. Barber, N.M. Anstey, T.W. Yeo); Gleneagles Hospital, Kota Kinabalu (T. William); Clinical Research Centre, Queen Elizabeth Hospital, Kota Kinabalu (T. William); QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia (B.E. Barber); Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA (J.S. Dumler); Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (T.W. Yeo); Communicable Disease Centre, Institute of Infectious Diseases and Epidemiology, Tan Tock Seng Hospital, Singapore (T.W. Yeo); Duke University, Durham, North Carolina, USA (M.E. Reller); Duke Global Health Institute, Durham (M.E. Reller)

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Table 1

Serologic and molecular detection of confirmed rickettsioses in a prospective cohort study of acute febrile illness attributable to rickettsioses, Sabah, East Malaysia, 2013–2015*

Confirmed rickettsial infections OT SFGR TGR Total
Confirmed age indeterminate (acute or past); acute-phase or convalescent-phase IgG titer >160,† n = 354 96 (27 [23–32]) 26 (7 [5–11]) 25 (7 [5–10]) 126 (36 [31–41])
Confirmed past infection; acute-phase IgG titer >160 with stable or decreasing paired titer,‡ n = 145
 13 (9 [5–14])
 4 (3 [1–7])
 4 (3 [1–7])
 17 (12 [7–18])
Confirmed rickettsial infection, acute
All acute confirmed,§ n = 378 26 (7 [5–10]) 18 (5 [3–7]) 7 (2 [1–4]) 49 (13 [10–17])
>4-fold rise in IgG titer,§ n = 145 25 (17 [12–24]) 10 (7 [4–12]) 5 (3 [1–8]) 38 (26 [20–34])
With seroconversion¶ 13 (9 [5–14]) 9 (6 [3–11]) 2 (1 [<1–5]) 22 (14 [9–20])
PCR positive,# n = 319 1 (<1 [0–2]) 8 (2 [1–5]) 2 (1 [0–2]) 11 (3 [2–6])
Copy number/mL, mean
 5,164
 482
 3477
Confirmed rickettsial infection, probable acute
All probable acute, n = 354
 58 (16 [13–21])
 12 (3 [2–6])
 16 (5 [3–7])
 77 (22 [18–26])
Paired serum samples
2-fold IgG titer rise to >160,** n = 145
 6 (4 [2–9])
 1 (1 [<1–4])
 2 (1 [<1–5])
 7 (5 [2–10])
Single serum samples
Acute-phase IgG >160,†† n = 197 45 (23 [18–29]) 8 (4 [2–8]) 12 (6 [4–10]) 60 (30 [24–37])
Convalescent-phase IgG >160,‡‡ n = 12 7 (58 [32–81]) 3 (25 [9–53]) 2 (17 [5–45]) 10 (83 [55–95])

*Values are no. (% [95% CI]) unless otherwise indicated. Total does not equal sum of individual infections because some of the individual infections are co-infections. OT, Orientia tsutsugamushi; SFGR, spotted-fever group rickettsiosis; TGR, typhus-group rickettsioses.
†Includes 18 patients with serologic evidence of OT/SFGR (6); OT/TGR (8); SFGR/TGR (1); OT/SFGR/TGR (3).
‡Includes 3 patients with serologic evidence of OT/TGR (2) and OT/SFGR/TGR (1).
§Includes 2 co-infections: 1 patient positive for OT and SFGR (both with acute-phase IgG titer of 40 and convalescent-phase titer of 320) and 1 patient for OT and TGR (both with acute-phase IgG titer of 40 and convalescent-phase titer 160).
¶Includes 1 patient each with serologic evidence of OT/TGR and OT/SFGR.
#No PCR-positive patients were confirmed also by paired IgG serology; 8 patients had acute-phase serum samples, and 1 TGR PCR-positive patient had IgM 2,560.
**Includes 2 patients with 2-fold IgG titer rises to OT and TGR
††Includes 3 patients positive for OT and TGR and 2 patients positive for OT and SFGR
‡‡Includes 1 patient each with serologic evidence of SF/TG and OT/TG.

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Page created: April 28, 2020
Page updated: June 18, 2020
Page reviewed: June 18, 2020
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