An aggressive and drug resistant version of the hospital superbug MRSA is spreading through the gay community in San Francisco. The infection rate is doubled in areas with a high gay population compared to the whole of the city. A study in Annals of Internal Medicine raised the alarm but some newspapers were way over the top reporting this comparing it to the HIV epidemic. Although the outbreak is worrying because of the high drug resistance of the MRSA strain involved and the HIV status of the community no way is it comparable to HIV. The infections are skin infections and there are still drugs to treat them as well as surgical methods.
We are all familiar with the ‘MRSA hospital superbug’ endemic in hospital wards, scourge of health systems. We are less familiar with community acquired MRSA (CA-MRSA), the bug causing the outbreak in San Francisco. It emerged about a decade ago and doctors coined its name when people began turning up in hospital already infected with MRSA rather than getting it while they were there.
CA -MRSA are slightly different from their hospital cousins, the strains are more aggressive and they produce toxins and more virulence factors. CA-MRSA cause skin and soft tissue infections but they are less drug resistant than the hospital types. The infection passes between people by skin contact. A single strain of CA-MRSA called USA300 spread across the USA and Canada recently and is responsible for a big increase in the number of skin infections (1).
Several groups seem disproportionately affected by USA300 including military recruits and prisoners and those playing contact sports. Another set of people who are affected appear to be poorer people, living in overcrowded conditions (2). Skin contact, skin damage, and poor hygiene seem to be risk factors for the illness.
Why gay men?
The San Francisco strain is a multiple drug resistant strain of USA300. Why should gay men be suffering? Is it because they are immunocompromised through HIV infection? Well the paper did find an association with HIV infection but it also found a separate association with being actively gay. Heterosexual spread has also been reported (3). So I think it is becoming clear CA-MRSA can be spread sexually.
How to prevent it?
It’s down to hygiene again! Good personal hygiene will help prevent catching the disease. Taking a shower with soap and water after activities that involve skin contact is enough to stop the spread of CA-MRSA, according to Diep the lead researcher on the gay study. Being careful to clean wounds and cover them will also help.
Carriage of this strain by people who don’t get sick could be an issue in controlling the disease. About one third of the population carry Staphylococcus aureus although only a tiny percentage of those people ever get ill from it. CA-MRSA could be unknowingly spread this way and it could develop drug resistance if those carriers are exposed to antibiotics.
Doctors need to be cautious prescribing drugs for this disease, to slow the spread of drug resistance as much as possible.
Selected references from Global Health:
1. Skin and soft tissue infections caused by methicillin-resistant Staphylococus aureus USA300 clone. Johnson, J. K. , Khoie, T. , Shurland, S. , Kreisel, K. , Stine, O. C. , Roghmann, M. C. Emerging Infectious Diseases, 2007, Vol. 13, No. 8, pp. 1195-1200, 23 ref.
2. Community-Associated Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infections at a Public Hospital. Do Public Housing and Incarceration Amplify Transmission? Bala Hota, MD, MPH; Charlotte Ellenbogen, MD; Mary K. Hayden, MD; Alla Aroutcheva, MD, PhD; Thomas W. Rice, PhD; Robert A. Weinstein, MD . Arch Intern Med. 2007;167:1026-1033.
3. Cook HA et al. Heterosexual transmission of community-associated methicillin-resistant Staphylococcus aureus. Clinical Infectious Diseases, 2007, Vol. 44, No. 3, pp. 410-413, 23 ref.