Purpose
- This report summarizes illnesses reported to the National Typhoid and Paratyphoid Fever Surveillance System (NTPFS) in 2020.
- Data include demographic and clinical characteristics, international travel, vaccination status, antimicrobial resistance and more.
Surveillance
JurisdictionsA reporting at least one case of Salmonella enterica serotype Typhi, Paratyphi A, Paratyphi B [tartrate negative], or Paratyphi CB to NTPFS during 2020 are shown in Figures 1 and 2. The surveillance system case definitions changed in 2019:
- 157 Salmonella Typhi cases were reported by 26 jurisdictions (Figure 1).
- 48 Salmonella Paratyphi casesC were reported by 19 jurisdictions (Figure 2).
Salmonella Typhi and Paratyphi are bacteria that cause severe and occasionally life-threatening bacteremic illness known as typhoid fever and paratyphoid fever, respectively. This report summarizes all cases of bacterial infection, including those that may be asymptomatic or have atypical clinical presentation.
Figure 1. Salmonella Typhi cases by jurisdiction, 2020 (n=157)
Figure 2. Salmonella Paratyphi cases by jurisdiction, 2020 (n=48)
Demographic and Clinical Characteristics of Patients
Demographic and clinical characteristics of patients with Salmonella Typhi and Paratyphi infections are shown in Tables 1 and 2.
- The median age of patients with Salmonella Typhi infections was 26 years (range 0–85)
- The median age of patients with Salmonella Paratyphi infections was 24 years (range 2–73)
- There were no deaths among patients with Salmonella Typhi or Paratyphi infections.
| Characteristic (number with data available) | Number | Percent |
|---|---|---|
| Age group, years (n = 154)
<1 |
1 |
<1 |
| 1–4 | 23 | 15 |
| 5–14 | 28 | 18 |
| 15–24 | 19 | 12 |
| 25–44 | 47 | 31 |
| 45–64 | 28 | 18 |
| 65+ | 8 | 5 |
| Female (n = 156) | 74 | 47 |
| Food handler (n = 98) | 4 | 4 |
| Outbreak-associated (n = 128) | 3 | 2 |
| International travel1 (n = 149) | 113 | 76 |
| Vaccinated2 (n = 92) | 6 | 7 |
| Specimen source (n = 145) | ||
| Blood | 124 | 86 |
| Stool | 19 | 13 |
| Other | 2 | 1 |
| Hospitalizations3 (n = 154) | 126 | 82 |
| Deaths (n = 141) | 0 | 0 |
1Travel destinations are shown in Table 3a.
2Received typhoid fever vaccination within five years before onset of illness; of the six cases in vaccinated persons, four received only the Vi capsular polysaccharide vaccine (ViCPS). Vaccine type was not reported for the other two cases.
3Median length of hospitalization was six days.
| Characteristic (number with data) | Number | Percent |
|---|---|---|
| Age group, years (n = 47)
<1 |
0 |
0 |
| 1–4 | 3 | 6 |
| 5–14 | 4 | 9 |
| 15–24 | 12 | 25 |
| 25–44 | 20 | 43 |
| 45–64 | 2 | 4 |
| 65+ | 6 | 13 |
| Female (n = 48) | 27 | 56 |
| Food handler (n = 27) | 1 | 4 |
| Outbreak-associated (n = 37) | 0 | 0 |
| International travel1 (n = 46) | 35 | 76 |
| Specimen source (n = 44) | ||
| Blood | 35 | 80 |
| Stool | 6 | 14 |
| Other | 3 | 7 |
| Hospitalizations2 (n = 48) | 37 | 71 |
| Deaths (n = 43) | 0 | 0 |
1Travel destinations are shown in Table 3b
2Median length of hospitalization was four days.
International Travel
- Among the 149 patients with Salmonella Typhi infections whose travel histories were reported, 113 (76%) reported traveling or living outside the United States in the 30 days before illness.
- Among the 46 patients with Salmonella Paratyphi infections whose travel histories were reported, 35 (76%) reported traveling or living outside the United States in the 30 days before illness.
- Among patients reporting international travel, 99 (66%) patients with Salmonella Typhi infections and 33 (94%) patients with Salmonella Paratyphi infections reported travel to a single destination (Tables 3a and 3b). More than 75% of patients with either pathogen reported travel to India or Pakistan.
- 54 (48%) patients with Salmonella Typhi infection and 16 (64%) patients with Salmonella Paratyphi infection reported visiting friends or relatives, which was the most commonly reported reason for international travel.
1Philippines (2), Ghana (1), Nigeria (1), Thailand (1)
Typhoid Fever Vaccine
Figure 3. Percentage of patients with Salmonella Typhi infection (n=92) who reported receiving a typhoid fever vaccine in the five years before illness, by year, 2016–2020
This figure excludes patients whose typhoid vaccination status was unknown or not reported (n=65).
National Notifiable Diseases Surveillance System
The National Notifiable Diseases Surveillance System (NNDSS) collects and compiles reports of nationally notifiable infectious diseases, including Salmonella Typhi and Paratyphi cases.
The figure below presents a comparison of Salmonella Typhi case reports submitted to NTPFS and NNDSS in the past five years. Reports submitted to NNDSS, but not NTPFS, can include clinically compatible cases that are epidemiologically linked to a confirmed case but are not laboratory-confirmed.
Comparisons for Salmonella Paratyphi are not provided because, although it was nationally notifiable, NNDSS does not report subtyping information for this condition.
Figure 4. Number of Salmonella Typhi cases reported to NNDSS and NTPFS, by year, 2016–2020
Antimicrobial Resistance
The National Antimicrobial Resistance Monitoring System (NARMS) monitors antimicrobial resistance among enteric bacteria (including Salmonella enterica serotypes Typhi and Paratyphi A, Paratyphi B, and Paratyphi C) from humans.1
Among Typhi, decreased susceptibility to ciprofloxacin (DSC) (minimum inhibitory concentration ≥0.12 µg/mL) has been associated with fluoroquinolone treatment failure. Multidrug-resistance (MDR) is defined as resistance to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole.
Among Salmonella Typhi isolates during 2020:
- 86% had DSC
- 25% were MDR
- 26.2% were resistant to three or more classes of antibiotics
- 19.4% were resistant to ceftriaxone
Among Salmonella Paratyphi A isolates during 2020:
- 99% had DSC
- No isolates were MDR
- No isolates were resistant to three or more classes of antibiotics
- No isolates were resistant to ceftriaxone
Data on resistance are available in NARMS Now, an interactive tool containing antibiotic resistance data from bacteria isolated from humans.
Outbreaks
The Foodborne Disease Outbreak Surveillance System (FDOSS) collects reports of foodborne disease outbreaks from local, state, tribal, and territorial public health agencies.
The Waterborne Disease and Outbreak Surveillance System (WBDOSS) collects reports of waterborne disease outbreaks associated with drinking and recreational water from local, state, tribal, and territorial public health agencies.
In 2020, there were no outbreaks of typhoid fever or paratyphoid fever.
- Includes all 50 states and District of Columbia.
- Two pathotypes of Paratyphi B are recognized, differentiated by the ability to ferment tartrate. The pathotype designated serotype Paratyphi B is unable to ferment tartrate; it causes paratyphoid fever. The other pathotype is designated Paratyphi B var. L(+) tartrate+; it can ferment tartrate and causes uncomplicated gastroenteritis. Only isolates laboratory-confirmed as not able to ferment tartrate are included in this annual summary. Many reports of Paratyphi B detection do not include this information.
- Zero cases of Salmonella serotype Paratyphi C and eleven cases of Salmonella Paratyphi without a specified serotype reported.