Epidemiologic Surveillance of ZIKV Infection and the Guillain–Barré Syndrome in Colombia

Figure 1. Figure 1. Cases of ZIKV Infection and the Guillain–Barré Syndrome in Colombia. Panel A shows a map of Colombia with Neuroviruses Emerging in the Americas Study (NEAS) participating sites in the context of the Zika virus (ZIKV) infection outbreak. Numbers of confirmed cases of ZIKV infection from epidemiologic week 32 of 2015 through week 12 of 2016 are shown. Panel B shows the cases of the Guillain–Barré syndrome that were diagnosed in parallel with ZIKV cases reported to the Colombian National Institute of Health and epidemiological surveillance system in Colombia from October 2015 through March 2016.

From October 2015 through March 2016, there were 2603 laboratory-confirmed ZIKV infections in Colombia and more than 58,790 suspected cases. In addition, there were 401 patients with a neurologic syndrome who had a history of ZIKV infection; 270 of the cases (67%) corresponded to the Guillain–Barré syndrome18 (Figure 1). On the basis of data from the registry of individual records of health care services, the INS estimated that approximately 250 cases of the Guillain–Barré syndrome per year occurred in the whole country between 2009 and 2015, for a mean of approximately 20 cases per month (unpublished data). The frequency was increased relative to that baseline rate during the ZIKV outbreak, during which more than 270 cases of the Guillain–Barré syndrome were registered up to epidemiologic week 12 of 2016, for a mean of approximately 90 cases per month.19 (In a given year, epidemiologic week 1 ends on the first Saturday in January, as long as it falls at least 4 days into the month.) According to surveillance data from the INS, DENV had circulated in Colombia during the last decade and caused periodic outbreaks. A chikungunya virus outbreak occurred in the region during most of 2015 (see the Supplementary Appendix). However, it was not until the end of 2015 and the beginning of 2016 that ZIKV was first introduced to the region, and this period coincided with the first documented increase in the incidence of the Guillain–Barré syndrome (Figure 1).

Clinical Features

Table 1. Table 1. Clinical and Demographic Characteristics of the 68 Patients with the Guillain–Barré Syndrome.

A total of 68 patients who fulfilled the Brighton criteria for the Guillain–Barré syndrome and related variants and presented to the participating centers were included: 56 patients (82%) fulfilled level 1 or 2 criteria on the basis of evidence from CSF analysis, neurophysiological studies, or both. Four patients (6%) had the Miller Fisher syndrome, and 2 patients (3%) had other Guillain–Barré syndrome variants (bilateral facial palsy with areflexia and a pure sensory syndrome). The median age of the patients was 47 years (interquartile range, 35 to 57), 38 patients (56%) were male, and 61 patients (90%) were of mixed race. A total of 66 patients (97%) had symptoms of ZIKV infection in the 4 weeks preceding the onset of neurologic symptoms (Table 1, and Table S1 in the Supplementary Appendix). Two patients did not report having had any systemic symptoms before the onset of the Guillain–Barré syndrome but were residents of a region affected by the ZIKV infection outbreak. The median duration of symptoms of ZIKV infection was 4 days; the condition manifested mainly with fever (in 69% of the patients), rash (59%), headaches (34%), myalgias (34%), nonpurulent conjunctivitis (25%), and arthralgias (22%). The median time between the onset of the ZIKV infection symptoms and the onset of the Guillain–Barré syndrome was 7 days (interquartile range, 3 to 10).

Table 2. Table 2. Clinical and Laboratory Findings in the 68 Patients with the Guillain–Barré Syndrome.

The clinical and laboratory features of the patients with the Guillain–Barré syndrome are summarized in Table 2, and in Table S2 in the Supplementary Appendix. The symptoms at presentation included limb weakness (97%), paresthesias (76%), and facial palsy (32%). A total of 56 patients (82%) reported an ascending pattern of weakness. On neurologic examination, the median Medical Research Council (MRC) sum score (which indicates muscle strength in 12 different muscle groups and ranges from 0 to 60, with higher scores indicating more preserved muscle strength) was 40 (interquartile range, 26 to 47).20 Cranial neuropathies were present in 43 patients, with bilateral facial palsy being the most common (in 50% of the 68 patients). Autonomic dysfunction was present in 21 patients (31%). A total of 40 patients (59%) were admitted to intensive care units, and 31% of all patients required mechanical ventilation. Treatment was administered to 46 patients (68%); intravenous immune globulin was the most commonly used treatment (62% of the 68 patients). Three patients (4%) died after respiratory failure and sepsis. The median modified Rankin score (which indicates the severity of disability and ranges from 0 to 6, with 0 indicating no symptoms and 6 indicating death) at nadir was 4 (interquartile range, 3 to 5).

Nerve-conduction studies and electromyography were performed with the use of standard techniques in 46 patients (68%). In accordance with published criteria,9,10 36 patients (78% of the 46 patients) were determined to have the AIDP subtype of the Guillain–Barré syndrome, 1 patient (2%) had the acute motor axonal neuropathy (AMAN) subtype, and 4 patients (9%) had equivocal studies that did not allow a subtype classification (Table 2). No abnormalities were noted in hematologic testing performed at admission. CSF analysis was performed in 55 patients (81%); the median white-cell count was 0 cells per cubic millimeter (interquartile range, 0 to 2.5), and the median protein concentration was 116 mg per deciliter (interquartile range, 67 to 171). A total of 45 patients (82%) had albuminocytologic dissociation in CSF, indicated by increased protein levels (>52 mg per deciliter) in the absence of pleocytosis (<10 cells per cubic millimeter).

Laboratory Tests for ZIKV Infection

Figure 2. Figure 2. Laboratory Testing and Temporal Profiles of Illness in 42 Patients with the Guillain–Barré Syndrome during the ZIKV Infection Outbreak in Colombia. Panel A shows the results of testing for flavivirus infection in various biologic samples from the 42 patients who underwent laboratory testing. Results of TaqMan reverse-transcriptase (RT)–polymerase-chain-reaction (PCR) assays for ZIKV and of IgM and IgG enzyme-linked immunosorbent assays for antiflavivirus antibodies are shown for each patient. The diagnosis of ZIKV infection was defined as definite (positive real-time RT-PCR assay for ZIKV RNA in blood, CSF, or urine), probable (positive enzyme-linked immunosorbent assays [ELISAs] for antiflavivirus antibodies in the cerebrospinal fluid [CSF], serum, or both but negative results of RT-PCR for ZIKV and for the four dengue virus serotypes), or suspected (clinical syndrome compatible with ZIKV infection with two or more features of the Pan American Health Organization case definition12 without laboratory confirmation). Panel B shows the temporal profile of clinical symptoms and results of ZIKV RT-PCR testing in patients with the Guillain–Barré syndrome. The bars represent the duration in days of the various periods of the clinical profile and the timeline of illness for each of the 42 patients who underwent virologic testing. The period of systemic symptoms of ZIKV infection in some patients overlaps with or is immediately followed by the onset of neurologic symptoms; in other patients, there is an asymptomatic period preceding the onset of neurologic symptoms. Two patients (Patients 29 and 40) died from respiratory and infection complications. Numbers of patients with definite ZIKV infection are shown in red.

Table 3. Table 3. Laboratory Studies for the Investigation of Flavivirus Infection in 42 Patients with the Guillain–Barré Syndrome.

Of the 68 patients, 42 (62%) underwent testing for ZIKV by RT-PCR in at least one of three biologic samples: urine (24 patients), serum (31 patients), and CSF (30 patients) (Figure 2 and Table 3, and Fig. S1 in the Supplementary Appendix). A total of 17 patients (40%) tested positive for ZIKV by RT-PCR; most of the positive results were in urine samples (16 patients). Three patients had positive ZIKV RT-PCR results in CSF (Fig. S2 in the Supplementary Appendix); only 1 patient had a positive result in serum, and this patient’s serum remained positive at 31 days after the onset of ZIKV infection (Patient 29 in Figure 2B). The median time from the onset of the symptoms of viral illness to the collection of the first ZIKV-positive urine sample was 16.5 days (interquartile range, 11.5 to 19.7), with 1 patient remaining positive at 48 days after onset (Patient 29 in Figure 2B). The results of RT-PCR for all four DENV serotypes were negative in the 39 patients tested.

ZIKV was cultured from the serum and urine of Patient 29 and from the urine of Patients 32 and 36 (Figure 2B) in C6/36 and Vero cell lines. The presence of ZIKV in the culture supernatants was confirmed by RT-PCR. Light microscopic imaging showed cytopathic changes consistent with flavivirus infection (Fig. S3 in the Supplementary Appendix). The profile of antiflavivirus antibodies is shown in Table 3 and Figure 2A, and in Table S3 in the Supplementary Appendix. A total of 32 of the 37 patients with the Guillain–Barré syndrome who were tested (86%) had evidence of a recent flavivirus infection, as indicated by the presence of cross-reactive IgM or IgG antiflavivirus antibodies. The pattern of expression of antiflavivirus antibodies stratified according to the results of the ZIKV RT-PCR is shown in Table S3 in the Supplementary Appendix. On the basis of clinical profiles and laboratory testing, the diagnosis of ZIKV infection was classified as definite in 17 patients, probable in 18 patients, and suspected in 33 patients (Table 1 and Table 3).

Temporal Profile of the Guillain–Barré Syndrome Cases with Laboratory Testing

Of the 68 patients with the Guillain–Barré syndrome, 42 underwent laboratory testing for the identification of ZIKV infection. Figure 2 shows the laboratory and clinical temporal profiles of the infection in these 42 patients. The period from the onset of symptoms of ZIKV infection to the onset of neurologic symptoms and the time to nadir is outlined for each case. Two patients did not have any symptoms of ZIKV infection preceding the neurologic symptoms, and 2 patients had simultaneous onset of ZIKV infection and neurologic symptoms. A total of 20 patients (48%) in this group had a rapid onset of neurologic symptoms without an asymptomatic period after ZIKV infection symptoms (parainfectious onset), whereas the other patients had a variable asymptomatic period between ZIKV infection and the onset of neurologic symptoms (postinfectious onset).