Ongoing Struggle with Meningitis W135 in Chile

On June 13, 2013, the Ministry of Health of Chile confirmed yet another case of Neisseria meningitidis serogroup W135 in a child from the Metropolitan Region. The child is the latest victim of the ongoing outbreak that hit the country in 2012. In 2013 alone, 24 cases and six deaths have been reported. The Minister of Health, Dr. Jaime Mañalich, has described W135 as "here to stay and very difficult to eradicate."

The severity of W135 has public health authorities concerned about the public health impact that an epidemic of W135 could have on the Chilean population.

Broadly, meningitis is characterized by the inflammation of membranes surrounding the brain and spinal cord. There are various types of meningitis that can affect humans: bacterial, viral, parasitic, fungal, and non-infectious. The most common type of meningitis in the United States, viral, is typically transmitted by enteroviruses that can spread easily due to contact with fecal matter (so, wash your hands) or respiratory secretions (and sneeze into your elbow). Often, its symptoms of fever, headache, and neck stiffness are mild and usually clear up without treatment. In contrast, bacterial meningitis may develop into meningococcal disease and lead to severe consequences, including death, if left untreated. Fortunately, we have vaccines that can protect against infection of many of the most common serogroups of meningitis, including W135.

A serogroup of bacterial meningitis, W135, shares many similarities with viral meningitis regarding symptoms, but markedly differ in transmission, incubation, and health consequences. Both viral and W135 strains can cause symptoms such as nausea, vomiting, diarrhea, headache, and sensitivity to light. W135 is harder to transmit than viral meningitis, however, requiring an extended period of close contact with an infected individual. Once transmitted, W135 can incubate earlier and longer (two to ten days) compared to viral serogroups (three to six days) until producing symptoms. While the effects of viral meningitis are short-term, W135 may cause long-lasting brain damage and hearing loss even after successful treatment.

The emergence of W135 in Latin America is a fairly recent development in the history of meningitis on the continent. Typically, serogroups B and C have been the most prevalent strains of bacterial meningitis in the region, while W135 only appeared in isolated international outbreaks. Meningitis-causing bacteria are separated into different serogroups depending on their structure. There are six different serogroups: A, B, C, W135, X and Y. A shift toward greater prevalence of W135 coincided with the outbreak of a hypervirulent strain of W135 associated with the 2000 and 2001 Hajj pilgrimage. As a result of the Hajj-related outbreak, many countries across the world saw a spike in W135 prevalence, including Chile, Argentina, and Brazil. By 2011, prevalence of W135 had risen from 0 percent in 2001 to 31 percent of meningococcal disease cases in Chile.

In response to the outbreak, the Ministry of Health initiated a “W135 Action Plan” in October 2012 to prevent further spread of the disease. The central pillar of the action plan is a mass vaccination campaign targeting children between nine months and five years of age, who are considered to be most vulnerable to the disease. The first phase of the campaign succeeded in vaccinating 100 percent of the target group across the country. Currently in its second phase, the campaign seeks to provide a second dose of vaccine to all children under the age of two. As of June 1, 2013, the Ministry of Health will expand the vaccination campaign to 30,000 health workers who come into frequent contact with children. The vaccination is being provided at no charge to these high-risk groups.

The government response to W135 is not without criticism. “The first phase of vaccination was chaos,” writes Dr. Francisca Rojas, a medical resident working in Santiago, Chile, in an email exchange. “In a few weeks, the government transitioned from a passive position (initially the government considered the vaccination unnecessary or its efficacy unproven) to mass vaccination,” she wrote. A shortage of vaccine in the public and private health sectors led to long lines outside health clinics and pre-schools where parents were told their children could be vaccinated. The situation was further aggravated by the rise in emergency room visits due to parents fearing their child was symptomatic of W135. Rojas blames media sensationalism and a lack of public education regarding W135 for the panic that ensued.

Despite criticism, the Ministry of Health sticks to the efficacy of their approach. The newly appointed Secretary of Health of the Bío Bío Region, Monica Campos Avello, credits the mass vaccination campaign for the absence of new cases in the Bío Bío Region since April. In an email exchange, Campos affirmed the acts of the Ministry of Health by writing, “The measures of the vaccination campaign have been correct. We haven’t had more cases, and we will continue vaccinating children year-round who turn nine months of age.”




“Meningitis 1-135: ISP confirma nuevo caso” La Tercera

“ISP confirma nuevo caso de meningitis cepa W-135” 24 Horas

Mañalich y aumento de casos de W-135: "El microbio llegó para quedarse y será muy difícil erradicarlo" La Tercera

“Meningitis” Centers for Disease Control and Prevention

“Meningococcal meningitis” World Health Organization 

“Plan de Accion W-135”  Chile Ministry of Health

Sáfadi, M., González-Ayala, S., Jäkel, A., Wieffer, H., Moreno, C., & Vyse, A. (2013). The epidemiology of meningococcal disease in Latin America 1945–2010: an unpredictable and changing landscape. Epidemiology and Infection, 141(03), 447-458.

“Amplían vacunación contra la meningitis W-135 a los funcionarios de la salud” Universia

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