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Measles eradication effort may be affected by HIV
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HIV may be playing a role in recent outbreaks of measles in sub-Saharan Africa, according to findings presented at the 48th Annual Meeting of the Infectious Diseases Society of America.
William Moss, MD, MPH, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, addressed global measles control in the HIV/AIDS era. “There has been a tragic resurgence of measles, particularly in sub-Saharan Africa,” he said. “For example, preliminary data indicate that the current measles outbreak in South Africa may be around 17,000 cases.”
Moss addressed the current status of global measles control, interactions between HIV and natural measles, the effect of HIV on measles vaccination and the effect of antiretroviral therapy on measles. He noted that the largest outbreaks of measles have been in countries with high HIV prevalence, including Lesotho, Malawi, South Africa, Zambia and Zimbabwe.
Moss said a fundamental issue is the decline in population immunity to measles, either community-wide or in pockets of individuals. Recent progress against the disease could be in jeopardy and he suggested that, as HIV rates rise and immunity is compromised, an increase in measles incidence may be imminent during the next few years.
“A key feature of measles epidemiology is that it is among the most highly contagious diseases,” he said. “It takes a small proportion of the population to be susceptible to get sustained measles transmission.”
Interactions with HIV
Despite this, Moss said controlling measles is much simpler than controlling HIV. He addressed the effect of HIV on clinical disease presentation and transmission of measles, and the effect of measles on the natural progression of HIV.
“Some children with HIV may present with a rash that looks like measles,” he said in a presentation. “The rash is manifestation of cell-mediated immunity.”
Moss said there are few data showing that mortality is increased among children with HIV who acquire measles. However, research that he and colleagues conducted in a cohort of children in Lusaka, Zambia, indicated about a 2.5-fold increased risk for in-hospital mortality among children with HIV and measles.
Regarding transmission rates, Moss said it is difficult to measure the infectiousness and infectious transmission of a disease such as measles. However, delayed clearance of measles virus RNA has been observed in children with HIV, which could indicate a longer infectious period than in those whose immune systems are not compromised.
“If [the children with HIV] are infectious for a longer period, then it follows that the transmission period could also be increased,” he said.
Conversely, Moss suggested that measles may actually lower HIV RNA levels. “We have seen this phenomenon, particularly in the cohort from Uganda that was published in the Journal of Infectious Diseases in 2002, but we do not have an explanation for it. It may involve the capacity of measles to inhibit lymphoproliferation.”
Vaccination rates
Moss highlighted four possible obstacles involved in measles vaccination in HIV populations:
- Lower vaccination rates in children born to women with HIV.
- More rapid loss of maternally-acquired antibodies.
- Higher rates of first- or second-degree vaccination failure.
- Potential for higher rate of adverse events.
“Children of mothers with HIV may be less likely to be vaccinated because they are more likely to be orphans, or those children may have chronic illnesses, which could in turn make mothers less likely to have them vaccinated,” he said. “But there is still not a lot of evidence.”
Moss said children born to mothers with HIV experience a more rapid loss of protective maternally-acquired antibodies, and primary or secondary vaccine failures tend to be higher in children with HIV than children who do not have HIV.
“As for adverse events, this is a difficult area to get data on,” he said. “We still do not know what the severe adverse event incidence is.”
For more information:
- Moss #150. Presented at: the IDSA 48th Annual Meeting. Oct. 21-24, 2010; Vancouver, B.C.