# High fever with rash: a case report of spotted fever group rickettsial infection at a construction site

## TL;DR

A construction worker with high fever and rash was diagnosed with a rare rickettsial infection using advanced sequencing, highlighting the need for careful diagnosis in similar cases.

## Contribution

Demonstrates the utility of metagenomic next-generation sequencing in diagnosing rare rickettsial infections in febrile patients with atypical presentations.

## Key findings

- Metagenomic next-generation sequencing identified Rickettsia rickettsii in a patient with unexplained fever and rash.
- Doxycycline treatment successfully resolved symptoms after initial antibiotic therapy failed.
- Rickettsial infections should be considered in febrile patients with poor living conditions and negative routine tests.

## Abstract

Spotted Fever Group Rickettsiae (SFGR) infection is one of the global public health threats. With the improvement of current hygiene conditions, the incidence of rickettsial infections has significantly decreased compared with previous years; however, in clinical practice, rickettsial infections should still be considered in the differential diagnosis of febrile cases of unknown etiology.

A construction worker, residing in crowded and poor sanitary conditions, presented with high fever and diffuse cutaneous rash, without reporting other associated discomfort. Empirical treatment with cephalosporin antibiotics failed to alleviate the symptoms. Given the unknown etiology of the patient’s high fever and rash, routine etiological tests yielded negative results, with concurrent abnormalities in the white blood cell differential count of the complete blood count. A strong suspicion of infection by an unusual microorganism prompted the performance of metagenomic next-generation sequencing (mNGS) on venous blood. This test identified infection with Rickettsia rickettsii belonging to the spotted fever group, confirming a rickettsial infection. Following the establishment of the etiology, the antimicrobial treatment regimen was adjusted, and the patient was administered doxycycline for antimicrobial therapy. After treatment, the patient’s body temperature returned to normal, the rash resolved, and the patient was discharged in a state of full recovery.

For patients working at construction sites with poor living conditions who present with high fever and rash but lack evidence of conventional microbial infection, clinicians should enhance their differential diagnostic capabilities and maintain vigilance for the occurrence of rickettsial infection.

The online version contains supplementary material available at 10.1186/s12879-026-12735-7.