Considerable overlap between HIV and shigellosis epidemics in the UK

Approximately a third of cases of non-travel-related Shigella dysentery in the UK involve HIV-positive patients, according to research presented to the annual conference of the British HIV Association in Manchester last week. Most of these cases were in men who have sex with men (MSM) living with HIV. The investigators believe their findings confirm previous research showing that HIV-positive MSM are a new high-risk group for Shigella, with the infection being transmitted sexually.

Shigellosis is a bacterial infection that can cause severe dysentery. Historically, cases in the UK have been associated with travel to low-income countries with poor hygiene. It is highly infectious and has very unpleasant symptoms, including fever, severe bloody diarrhoea and abdominal cramps. Complications can include dehydration, and more rarely, bacteraemia, Reiter’s syndrome (a type of arthritis that occurs when bacteria enters the body) and a syndrome that can lead to kidney failure.

Outbreaks of shigellosis have been documented in MSM since the 1970s. A new profile of patients with shigellosis is emerging in the UK and similar countries. Cases often involve HIV-positive MSM, reporting sexual activities such as rimming (anal-oral contact) and fisting, high numbers of sexual partners, dense sexual networks, 'chemsex' and attendance at sex parties. This risk profile overlaps with that for other emergent sexually transmitted infections in HIV-positive MSM, including hepatitis C virus (HCV), lymphogranuloma venereum (LGV) and resurgent syphilis.

Diagnoses of travel-related shigellosis in the UK have been increasing steadily since 2004, reaching a peak of approximately 700 cases in 2010 before falling to a little over 400 diagnoses in 2014.

Non-travel-related diagnoses overtook travel-related diagnoses in 2012 and over 800 non-travel-related cases of shigellosis were diagnoses in 2014.

A team of investigators from Public Health England used nationally collected surveillance data to determine the role of HIV in the UK’s ongoing shigellosis epidemic.

Information on all 10,027 shigellosis diagnoses made between 2003 and 2015 was obtained. This included date of diagnosis, age and association with travel. The investigators also obtained data on all 139,950 HIV cases diagnosed in the UK, including gender, sexuality, clinical data and date of diagnosis. The two datasets were anonymously linked, enabling the researchers to determine the proportion of shigellosis cases that involved patients with HIV, the proportion who were MSM and temporal trends in diagnoses.

Overall, 1184 (12%) shigellosis diagnoses were in patients with HIV. When diagnoses were broken down according to their association with travel, it was revealed that 1050 of these cases were non-travel-related and just 134 were related to travel.

Relatively few travel-related diagnoses involved HIV-positive men (5%) or women (1%).

But when non-travel-related cases were examined, it was shown that 30% of all diagnoses were in HIV-positive men and 2% involved HIV-positive women.

Closer analyses of non-travel-related cases in HIV-positive men showed that 94% involved MSM. Just under a half were taking HIV-therapy and 69% had a viral load below 400 copies/ml.

Diagnoses of non-travel-related shigellosis among HIV-positive men increased steadily from 55.5 per 100,000 diagnosed HIV population in 2005 to 364.4 cases per 100,000 by 2014. An especially sharp increase in diagnoses was recorded after 2011.

The investigators conclude that 30% of men diagnosed with non-travel associated  were diagnosed with HIV and most of these were MSM. The investigators recommend that all HIV-positive men presenting with lower gastrointestinal tract infections should be considered forshigellosis. They also believe their findings are consistent with current understanding about high-risk sexual behaviour among HIV-positive MSM.