HAVANA — An aggressive strain of the human immunodeficiency virus (HIV) has been identified in Cuba, confirming the fears of local clinicians who noted unusually rapid AIDS progressions in patients recently infected with HIV.
The new strain is a combination of three existing subtypes of HIV, and can progress to full-blown AIDS within three years, versus the usual mean of six to ten years.
HIV is a treatable, albeit incurable, infection if early antiretroviral medication is administered to delay or prevent the onset of AIDS and the depletion of the body’s immune function. But a strain with such rapid progression to AIDS means that therapy may be initiated too late, leading to higher rates of AIDS-related mortality.
Detailing their findings, researchers from the Rega Institute for Medical Research in Belgium declared that the new strain has become “epidemic”¹ among newly-infected patients in Cuba, raising concerns among AIDS researchers that such mutated viruses could be more difficult to diagnose, and may be more resistant to therapy.
How did this happen? HIV, like many retroviruses, is known to mutate and create new versions of itself during viral replication. Over 60 strains of HIV type 1 exist as a result of natural mutations, but in some cases, mutations make the virus less fit and less virulent.
The current strain, called CRF19, is different. As a combination of HIV subtypes D, A and G, it is particularly fit and drives a much higher viral load in the blood, leading to a more pronounced immune response and a quickened onset of AIDS.
All patients with the current strain who progressed to AIDS had tested HIV-negative between one and two years before diagnosis.
HIV infects cells by attaching to a site on the cell’s surface called a co-receptor, and the transition to AIDS usually occurs after several years when the virus switches from co-receptor CCR5 to co-receptor CXCR4. The new strain makes the switch more rapidly.
Researchers noted that patients with the CRF19 strain reported instances of unprotected sex with multiple partners, which points to the likelihood that the strain developed as a result of multiple co-infections with different viral subtypes.
The takeaway: The rapid progression to full-blown AIDS, by which point antiretroviral therapy is less effective, is concerning, considering that most people may not recognize that they are infected with HIV, and may test negative for the virus during early infection periods.
Additionally, the higher viral load associated with CRF19 makes infected, untreated, patients more likely to pass on the strain to their partners through unprotected sex.
With the recent relaxation of travel restrictions between Cuba and the US, some are concerned about the likelihood of the spread of the CRF19 strain to the US mainland and the wider Caribbean region.
Speaking to the Miami Herald, Hector Bolivar, an infectious disease specialist at the University of Miami Miller School of Medicine, said: “This is something that hasn’t been seen before this clearly.” “We knew that sooner or later we were going to face this locally [and] Cuba is local for Miami. We may see similar situations here in Miami in the future, and that’s something I’m concerned about.”
Encouragingly, CRF19 is responsive to most antiretroviral drugs, but its discovery in this hemisphere and the extent of its spread underscores the need for frequent, early HIV testing, and enhanced access to HIV prophylaxis methods in the region.
¹ As quoted by researchers.