|Year : 2017 | Volume
| Issue : 5 | Page : 447-452
Measles outbreak in adults: A changing epidemiological pattern
Swati Bajaj1, Pranjal Bobdey2, Neha Singh3
1 Department of Community Medicine, Armed Forces Medical College, Pune, Maharashtra, India
2 Department of Community Medicine, Command Hospital, Southern Command, Pune, Maharashtra, India
3 Department of Community Medicine, Army College of Medical Sciences, New Delhi, India
|Date of Submission||05-Mar-2017|
|Date of Acceptance||06-May-2017|
|Date of Web Publication||14-Nov-2017|
Station Health Organisation, 1-Napier Road, Wanawadi, Pune - 411 040, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Thirty-one cases of fever with rash were reported among students of a college in Pune, India, from March to May 2014. The clinical profile was similar to that of measles and 7 of them tested positive for measles-specific immunoglobulin M (IgM). An outbreak of measles was declared, and epidemiological investigation was carried out to assess the situation and suggest preventive measures. Methods: An epidemiological case sheet filled for each case to identify the source and likely contacts. Medical and administrative authorities were sensitized about the increase in incidence and clustering of cases. A surveillance system was set up for detection of new cases and follow-up of contacts. Throat swabs and blood samples from 12 cases were tested by ELISA method for commonly occurring viral exanthematous fevers to confirm the diagnosis and 7 were positive for measles-specific IgM antibody. Preventive measures were advised to control the outbreak. Results: A total of 31 cases of fever with rashes were reported among students of a college in Pune, India, during the months of March–May 2014. Most of the students were in the age group of 18–24 years. Samples from 12 cases were sent for testing and 7 tested positive for measles-specific IgM antibodies. Seven cases were epidemiologically linked to a lab-confirmed case. All cases had fever, maculopapular rash, and sore throat and gave a history of vaccination for measles in childhood. Conclusion: An epidemiological investigation was carried out for outbreak of measles in a young adult population of college students from Pune. It is reported that, with increase in overall coverage of vaccination, there is a rise in incidence of measles in vaccinated individuals. The age profile also shifts to higher age groups. Investigation of such outbreaks provides an opportunity to identify high-risk groups, changes in measles epidemiology and weaknesses in the routine immunization programs.
Keywords: Changing epidemiology, measles outbreak, vaccination strategies
|How to cite this article:|
Bajaj S, Bobdey P, Singh N. Measles outbreak in adults: A changing epidemiological pattern. Med J DY Patil Univ 2017;10:447-52
| Introduction|| |
Measles is one of the acutely infectious diseases caused by a specific virus of the group myxovirus. It is a leading cause of the childhood morbidity and mortality in the developing world. Since the introduction of effective measles vaccine, the epidemiology of measles has changed in both developed and developing countries. Until 2008, India was the only nation among 193 member nations of the World Health Organization to make provision for only single dose measles vaccine in their National Immunization Schedule, whereas all other nations opted for two doses of measles vaccine. In fact, in case-based measles surveillance in Pune, it was observed that in approximately 40% of confirmed measles cases; the patient acquired the disease despite being immunized with a single dose of measles vaccine.
Outbreaks of measles are generally due to the accumulation of measles-susceptible persons, including both unvaccinated children and those who were vaccinated but failed to seroconvert. As vaccine coverage has increased, there has been a marked reduction in measles incidence in the pediatric age group; but at the same time, the average age, at which measles infection occurs, has significantly increased.
The immunity conferred by vaccination against measles is considered to persist for at least 20 years and is generally thought to be lifelong for most individuals. This article investigates an outbreak of measles in a young adult population with the aim to bring out the epidemiological shift of measles to older age of 18–24 years.
| Methods|| |
A retrospective cohort study was conducted to investigate the outbreak of measles among young medical students staying in the hostel of a college of Pune, India.
On March 1, 2014, a young adult female, student of a college from Pune, India, reported with complaints of fever, sore throat and running nose accompanied by maculopapular rash on face and body. Although she did not have a clear history of exposure to a case of measles, she had gone to West Bengal for a family function from 22 to 28 February 2014 where she came in contact with a large number of people. She tested negative for measles-specific immunoglobulin M (IgM) antibody. Ideal days of collection of the sample and the window period when the serum sample will show positive result is 4th day to 28th day after onset of rash. If this is not adhered to a positive case will not show the presence of IgM antibodies.
Case 2 was admitted on March 13, 2014, with similar prodromal symptoms of fever and sore throat for 3–4 days and maculopapular rash starting from face and then appearing on trunk and arms. The patient gave a history of contact with the first case on March 1, 2014, and tested positive for measles-specific IgM antibody. A total of 31 cases with similar symptoms were admitted from the same setting from March 1, 2014, to May 10, 2014. All cases were from the same college and most of them were staying in hostel. Throat swab from 12 cases was sent for laboratory confirmation to the National Institute of Virology (NIV), Pune. Of these, 7 cases were positive for measles by ELISA method and 5 were negative. Of the remaining the cases, 7 were epidemiologically linked to a laboratory-confirmed case showing an epidemiological correlation in terms of time, place and person, 5 were discarded and 12 were clinically confirmed cases.
A clinical case of measles is defined as per WHO case definition as any person with fever, maculopapular rash, cough, coryza, or conjunctivitis. An epidemiologically linked case is defined as direct contact with another laboratory confirmed measles case, in which rash onset occurred 7–18 days before the present case. If a suspected measles case has not been completely investigated, for any reason, it is considered clinically confirmed and that which has been completely investigated, and lacks serological evidence of measles virus infection is classified as discarded. Since the cases were clearly in excess as compared to previous 2 years during the same time and same place, it was termed as an outbreak. The outbreak was laboratory confirmed as 7 samples tested positive for measles-specific IgM antibody.
Cases were confirmed as per laboratory criteria for diagnosis given in WHO guidelines as the presence of measles-specific IgM antibodies. Blood samples and throat swabs collected from 12 of the patients were also sent to the NIV, Pune, for confirmation of diagnosis.
Surveillance to identify cases in the college began immediately. Both active and passive surveillance was carried out for early detection and isolation of cases. Active surveillance was conducted by daily checking of all inmates of the hostel for prodromal symptoms and/or rash. Some senior students were designated for this task in the hostel. They conducted active search by checking the students daily and informing the medical authorities in case of any symptoms in a student. High index of suspicion was kept especially among individuals showing prodromal symptoms of body ache, malaise, fever, sore throat, coryza, and conjunctivitis. A floor in the hostel was earmarked for segregation of contacts, and any person showing symptoms was kept in isolation in separate room for observation. He/she was not allowed to visit any common areas such as mess and classes and food was served to them in the room. A notice was put up on the hostel notice board, notifying the students of the measles cases and encouraging those with prodromal symptoms to seek medical attention. The public health and administrative authorities received regular updates and enhanced surveillance was established in the general population. Hospital staff was sensitized to consider measles as a possible diagnosis in patients reporting with fever and rash.
Students were advised to ensure proper ventilation in their hostel rooms by keeping windows and ventilators open and switching on the fans. There was no overcrowding as each student had a separate room. Sun drying of linen and bedding was advised. Daily wet mopping of rooms, corridors, and washrooms with 5% Cresoli Black was done. Articles soiled with throat and nose secretions were disinfected and discarded in covered bins. Hand hygiene and personal hygiene were advised. The use of disposable tissue papers for coughing and sneezing and practice of frequent hand washing with soap and water or sterilizing agent was advised. Lecture on prevention of airborne infections and importance of early reporting of symptoms was taken for the students of the college. Health advisories were displayed on notice boards in the hostel premises and common areas such as mess, TV room, and library. No recommendations were made to provide measles vaccine to all the students. All students with symptoms of fever and rash were admitted in the isolation ward of the hospital. Standard precautions and disinfection were carried out in the hospital for admitted cases.
| Results|| |
A total of 31 cases were admitted with complaints of fever, sore throat and rash, including 10 females and 21 males. There were a total of 135 girls and 525 boys in the hostel. The incidence was 4.6%. [Table 1] shows the demographic profile of the cases. Maximum cases were in the age group of 18–20 years (58%) followed by age group of 21–24 years (39%) and one was 34 years of age. [Table 2] shows the history of contact, clinical profile, and vaccination status of the cases. History of contact with a previous case was present in 20 cases (65%), 9 cases (29%) did not give any history of contact and it was doubtful in 2 cases (6%). All cases had symptoms of fever, sore throat, coryza, and maculopapular rash. Five cases (16%) also had some vesicular eruptions. Conjunctivitis was not commonly seen and only 4 cases (13%) had this symptom. One case in the highest age group developed complications in the form of viral myocarditis but recovered completely. All cases gave history of immunization for measles vaccine as confirmed from their parents though no documentary evidence was checked. Since documentary evidence was not available, the vaccination status for these cases will be considered as “unknown.” [Table 3] shows the investigation results of the cases. 7 cases (23%) were laboratory confirmed for measles IgM antibody and 5 cases (16%) tested negative for measles IgM antibody. These cases were discarded. Laboratory tests were not done for 19 cases (61%), and they were confirmed based on their clinical profile and epidemiological linkage with a laboratory-confirmed case. The epidemic curve points toward a propagative outbreak as shown in [Figure 1].
| Discussion|| |
Outbreaks of air-borne infections are common in students staying in hostels due to higher chances of contact among them. In the present scenario, the affected population was that of young students of the same medical college, who had common lecture halls for attending classes and same lodging and dining facilities. A similar small measles outbreak occurred in Indiana in 2005, when an adolescent US citizen traveling in Europe became infected in Romania and exposed 500 people at a church gathering on her return. Thirty-four cases of measles were reported from this exposure and many were adults. As per data published by NIV in Indian J Med Res, altogether, 98 suspected measles outbreaks were reported from the 20 districts of Maharashtra between January and December 2013. From the 20 districts, 491 serum samples were received for the laboratory diagnosis at the Measles Laboratory, NIV, Pune. Of these 491 suspected measles cases, 253 were male and 238 were female cases. The majority of the suspected cases were grouped in 0–15 years (97.5%, n = 479) and the remaining 12 were >15 years old. Of these suspected cases, 126 had a history of at least one dose of measles vaccine as per the record or by the parents recall. Anne Schuchat, MD, Director of the CDC's National Center for Immunization and Respiratory Diseases said in a press briefing in 2015 that they were starting to see more adults get measles and spread it.
The likelihood of a measles outbreak occurring in a population following the introduction of the virus is based on susceptibility of the population and number of exposures to an infectious measles case among susceptible persons. In relatively closed populations such as schools, measles can be transmitted and an outbreak sustained through several generations, despite high levels of immunity, because of repeated exposures.,, As per a study on health science students at Manipal University, India, among the overall group, the prevalence of serological susceptibility to measles, mumps, rubella (MMR), and varicella were 9.5%, 32.0%, 16.6%, and 25.8%, respectively; and among the subgroup of vaccinated subjects, susceptibility to MMR and varicella were 7.9%, 34.7%, 10.7%, and 35.2%, respectively. Ongoing education is needed to prompt health-care providers to have a high index of suspicion for measles in young adults presenting with rash illness and upper respiratory tract symptoms. Most reported measles in adults is associated with transmission in college and university settings, where the frequency of exposure is high. In early 1988, an outbreak of 84 measles cases occurred at a college in Colorado in which over 98% of students had documentation of adequate measles immunity.
The cases in our study were tested for Chickenpox, Rubella, and Measles antibodies. Throat swabs and blood samples of 12 cases were sent to the NIV, Pune, for further investigations to determine the causative organism. Because viral isolation is technically difficult and is not widely available, serologic testing is the method most commonly used. The measles-specific IgM antibody assay, the test used most often, is almost 100% sensitive when done 2–3 days after the onset of the rash., In this study, measles antibody was measured by ELISA. Several investigators have reported that the plaque reduction neutralization assay is more accurate than ELISA in determining levels of protective antibody. One comparative study demonstrated that the positive predictive value of measles antibody detected by ELISA is high (98.7%), and the negative predictive value is somewhat lower (58.3%) than the positive and negative predictive values of the plaque reduction neutralization assay.
Most of the cases in this outbreak recovered completely within 4–5 days of the appearance of rash showing a low morbidity rate and low virulence of the organism. A modified form of measles can occur in people with some degree of passive immunity to the virus, including those previously vaccinated. The clinical manifestations vary, and the illness may not have the classic features of prodrome, rash and Koplik spots.
In the present scenario, only one case in the highest age group developed severe complications in the form of viral myocarditis but recovered completely. Complications of measles most often occur in patients under age 5 and over age 20. Complications most commonly involve the respiratory tract and central nervous system. The death rate associated with measles in developed countries is 1–3 deaths per 1000 cases; in developing countries, the rate of complications and the death rate are both appreciably higher, with malnutrition contributing significantly to the higher rate of complications.
All cases in our study gave a history of immunization with one dose of measles vaccine/MMR during their childhood. However, with no documentary evidence available, their status will be categorized as “unknown.” Previous coverage evaluation surveys have shown that mean national coverage with measles vaccine has never exceeded 70%. With 85% vaccine effectiveness for vaccination at 9 months, actual protection was offered to only 60% of annual birth cohorts (70% × 85% = 60%). In other words, at least 40% remained susceptible to measles. Because of the occurrence of measles cases in adolescents, young adults and adults, potentially susceptible people should be identified and vaccinated as per current guidelines. Two doses of live-virus measles vaccine are recommended for all healthy children before they begin school, with the first dose given at 12–15 months of age. The second booster dose of vaccine can be administered at 4–5 years of age. Waning immunity after vaccination occurs very rarely, with approximately 5% of children developing secondary vaccine failure 10–15 years after vaccination., As per CDC, all adults who are susceptible should receive at least one dose of measles vaccine. Adults at higher risk of contracting measles include students in high school and college, international travelers, and health-care personnel. For these adults, two doses of measles vaccine, at least 28 days apart, are recommended. Passive immunization with intramuscular immune globulin within 6 days of exposure can be used in selected circumstances to prevent transmission or to modify the clinical course of the infection. Immune globulin should not be used to control measles outbreaks. The study by Ehresmann et al. provides data to support the current CDC recommendation that mass revaccination of entire communities is generally not necessary for control of measles outbreaks, particularly for outbreaks involving predominantly adults.,
India has conducted measles catch-up campaigns as a part of global effort to reduce measles morbidity and mortality. Target age group of this campaign is 9 months to <10 years children irrespective of their previous measles vaccination status or measles infection. A follow-up campaign may be required to maintain high population immunity against measles besides maintaining high routine immunization coverage. The timing and need for a follow-up campaign will be determined by routine immunization coverage rates, the quality of the catch-up campaign and surveillance data.
- The findings of various studies have indicated the significance of waning of immunity (i.e., protective level of antibodies) over a period after receiving a single dose of measles vaccine. In fact, it has been shown that the levels of antibodies developed in response to the vaccine decline at a much faster rate than when naturally acquired
- Policy makers should think of introduction of measles vaccination to college going students in metropolitan cities, where students from various parts of India come for educational purposes. To achieve the nation's goal of measles elimination and bring about a significant reduction in measles-related deaths, the need of the hour is to maintain a high level of immunization coverage for the measles vaccine and to strengthen all the integral components of the national immunization programme
- Sensitizing health professionals to the need to conduct measles outbreak-based surveillance in all the states and union territories of India can also assist in reducing the incidence of the disease
- Improvement of all components of the measles immunization program such as infrastructure support, manpower and other resources, and laboratory assistance such as virological surveillance is necessary for the reduction of measles outbreak in children as well as in adult age group.
| Conclusion|| |
There were 31 cases of fever with rash reported among students of a college in Pune and 7 of them were laboratory confirmed cases of measles. Airborne infections spread rapidly among susceptible groups living in close contact mainly through the respiratory route, and secondarily through direct/indirect contact. They may assume the proportions of an outbreak/epidemic very rapidly in schools, training centres and other closed communities. Control is essentially by early detection, segregation of exposed groups, and finally by isolation of the affected persons. Concurrent disinfection aids in control of spread. Outbreak investigations are very useful for monitoring changes in measles epidemiology and identifying and correcting weaknesses that have led to outbreaks. The data collected through outbreaks provides critical information such as age distribution of measles cases and age-specific measles case fatality rates. Finally, further research is needed to better understand the changing measles epidemiology, including the role that young infants and older age groups play in sustaining measles virus transmission and in contributing to overall burden of disease.
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[Table 1], [Table 2], [Table 3]