Kaposi Sarcoma Virus From Donated Organs: A Fivefold Rise, 2021–2025

At a glance

• Known before: Kaposi sarcoma–associated herpesvirus (KSHV) causes Kaposi sarcoma and some lymphoproliferative disorders. In organ transplant recipients, it can come from a reactivated old infection, a new infection after transplant, or the donated organ itself.
• Found here: from January 2021 to September 2025, 46 cases of suspected donor-derived KSHV complications were reported in recipients, against nine in 2016–2020. Most donors and recipients were HIV-negative, and two thirds of donors had used drugs nonmedically, by inhalation or injection.
• What follows: clinicians caring for transplant recipients should keep KSHV in mind for prompt diagnosis and reporting, and donor screening tests could help limit harm.

The virus

KSHV, also called human herpesvirus 8, causes Kaposi sarcoma (KS); lymphoproliferative disorders such as multicentric Castleman disease and primary effusion lymphoma; and KSHV inflammatory cytokine syndrome (KICS), a recently described condition resembling severe sepsis. Transplant recipients take drugs that suppress immunity to prevent rejection, so infection can be severe or fatal. Yet donors and recipients aren't routinely tested for KSHV: few commercial tests exist and there are no agreed screening guidelines, though testing of deceased donors is required for certain other infections.

In 2021, CDC reported transmission through transplants from six donors investigated in 2018–2020; four of 14 infected recipients (29%) died.

What was found

Transplant centers must report suspected donor-derived infections or cancers to the Organ Procurement and Transplantation Network (OPTN), and CDC investigated every KSHV report, reviewing records and testing specimens.

• Scale: 185 organs from 46 deceased donors went to 153 recipients. The 46 reports were a rise of about 500% over the previous five years; investigating them found 28 more affected recipients, and follow-up continues.
• Donors: median age 38.5; 67% male; 33% men who have sex with men; 96% HIV-negative; 67% had used drugs by inhalation (methamphetamine, cocaine, marijuana or alkyl nitrates) or injection; 17% had been incarcerated. Of 29 tested after procurement, 25 (86%) were KSHV-positive.
• Recipients: median age 58.5; half male; 98% HIV-negative. 74 (48%) tested positive for KSHV after transplant.

Reports of donor-derived KSHV and the investigation of other recipients, January 2021–September 2025. CDC, MMWR.

By organ, recipients testing positive: lung 86%, liver 57%, heart 30%, kidney 22%.

Among the 74 infected:

25 of the 153 recipients (16%) have died; how much KSHV contributed is under investigation. The median time from transplant to first symptoms was 208 days.

Reports of suspected donor-derived KSHV in transplant recipients, January 2010–September 2025 (57 in all). CDC, MMWR.

Why it's rising

In the United States, KSHV has historically been linked to men who have sex with men and to people with HIV — but here, most donors and recipients were neither. Nonmedical drug use is increasingly recognized as a risk factor. The share of deceased donors who died of acute drug intoxication rose from 4% in 2010 to a peak of 17% in 2023, likely reflecting the opioid epidemic — though undisclosed sexual behavior may confound the link. Scarce commercial tests, especially serology, have hampered tracking.

What clinicians should do

• Suspect KSHV — including KICS, which can look like culture-negative sepsis — and consider testing when the donor has risk factors, the donor is found infected, or another recipient of the same donor's organs is infected.
• Test well: without tissue examination, use both molecular and serologic tests when possible, and at least serology — molecular tests can miss infection, and KSHV DNA appears in the blood only episodically.
• Report suspected donor-derived KSHV to OPTN promptly.

Limitations

• Only suspected cases were investigated, so some were likely missed.
• Donor histories came from next of kin, who may not know every behavior.
• Not every recipient had both kinds of test, and some declined testing, so infections may be undercounted.
• A donor's infection doesn't rule out reactivation or a new infection in the recipient; testing recipients' pre-transplant samples could clarify.

Perspective

Donor-derived KSHV is still uncommon. Transplants' benefits generally outweigh infection risks — donor-derived transmission affects fewer than 0.5% of recipients — and far more people wait for organs than there are organs. Organs from donors with infection risk factors, KSHV included, can still be used safely. The investigation continues, and CDC is working with partners to make transplantation safer.

Sources

Based on "Kaposi Sarcoma–Associated Herpesvirus Infection and Complications Among Solid Organ Transplant Recipients — United States, January 2021–September 2025," by Ian Kracalik and colleagues of CDC, transplant centers and universities, and the Donor-Derived KSHV Investigation Group, Morbidity and Mortality Weekly Report, CDC; a work of the United States government in the public domain.