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From July through October of 1997, Costa Rica experienced a measles with a total of 12 laboratory-confirmed. Ten clinically-confirmed measles cases were reported for the entire year. The following article summarizes the findings of the team that investigated the outbreak.
The measles elimination initiative was launched in Costa Rica in 1993, but only 75% vaccination coverage was achieved in children under 15 years of age during the attack phase (catch-up campaign). Since 1995, selective vaccination campaigns have been held annually, most recently in April 1997. The age for vaccination with measles-mumps-rubella (MMR) vaccine was 12 months of age prior to 1991, 18 months of age from 1991-1994, and 15 months of age from 1994 onward. In 1992, a booster dose was implemented at the age of 7 years (first grade of school). The last measles epidemic occurred from 1990 to 1992, producing more than 8,000 cases and 56 deaths. The last confirmed case of measles corresponds to that time.
From January through June of 1997, there had been 49 suspected measles cases reported. Of these, 38 were discarded, 10 were under investigation and one case was clinically confirmed.
Investigation
The first laboratory-confirmed measles case (index case), was a 27 year-old from the county of Liberia in the Northwest province of Guanacaste, who worked as a cook at a restaurant in the El Tamarindo beach, a tourist complex located approximately 60 km from Liberia with at least 60 hotels. The case had rash onset on 22 July 1997, accompanied by conjunctivitis and poor general condition. On 25 July, the patient developed a generalized maculopapular rash, and was admitted to Liberia Hospital for three days. A serum specimen from the patient tested positive for measles at the national laboratory (INCIENSA). The result was confirmed by the Measles Reference Laboratory of the Gorgas Center in Panama.
Twenty days prior to the illness, the patient had moved from Liberia to El Tamarindo beach to work in a restaurant. The patient was living in Santa Rosa, approximately 10 km from El Tamarindo, with a population of approximately 1,000. As cook, he did not have much contact with the restaurant's clients. Community investigation did not show any suspected measles cases in Santa Rosa. The patient does not remember being vaccinated against measles.
The second documented case, a woman 33 years of age, had rash onset on 11 August, and was hospitalized for five days. On 21 August, a third case was reported in a 12 month old child from Cuajiniquil in La Cruz county, who was hospitalized that same day in Liberia Hospital. The mother revealed that her child had previously been hospitalized on 8-9 August with asthmatic bronchitis. There were two additional cases in Cuajiniquil, in children 13 and 14 months of age, who had direct contact with this patient.
On 9 September, two more cases were reported in Liberia. One, a girl of 7 months, was hospitalized from 21 to 25 August, with viral meningitis in Liberia Hospital. Fever and rash began ten days after her discharge, on 2 September. The other case was a girl 6 months of age, for whom there was no determined source of infection. All cases in this series were confirmed by INCIENSA and the Gorgas Laboratory.
A detailed investigation took place from 4-8 October, 1997. An analysis of vaccination coverage showed that at least 3 of the 12 counties in the province of Guanacaste did not achieve the required coverage rates for measles (more than 90%) in children under 1 year of age in the last two years.
The epidemiological history of the index case indicates that he likely contracted the virus at El Tamarindo beach, a popular tourist attraction. Most visitors come from Europe, North America, Canada, South America, and some from Central America. The largest hotels register between 35,000 and 40,000 tourists per year.
All contacts of the index case at the restaurant were interviewed without result. Next, selected hotels were visited. The manager of one said that in early July, three Brazilian tourists were lodged, one of which presented fever upon arrival and subsequently rash appeared. A physician diagnosed measles but did not report the case. The three guests left the hotel around 19 August 1997. This hotel is less than 100 meters from the restaurant where the index case worked, and it is probable that the tourists went to eat in that restaurant. Two other suspected measles cases were found during the active search.
PAHO contacted the Ministry of Health of Brazil to investigate the suspected measles case from this Brazilian tourist. The case was confirmed as measles and it was also determined that the case was from the Sao Paulo area.
An analysis was carried out of all patients that entered Liberia Hospital from mid-July through the end of September, to determine whether these patients had disseminated the virus to other regions of the country upon leaving the hospital. It was found that patients from all 12 counties of the Guanacaste province had been hospitalized, as well as people from five other counties of the country, including San José, and two patients from Nicaragua.
Control Measures
Selective vaccination was carried out in the county of Liberia targeting the entire population under 15 years of age. A national vaccination campaign against measles was implemented on 20 October 1997.
All countries in the Region of the Americas were alerted, particularly those in Central America, of the high risk of importations, especially in areas with low vaccination coverage.
Conclusions
Measles virus circulated in the province of Guanacaste in July to October 1997. The first case was presented in an adult of 27 years, hospitalized on 25 July in Liberia Hospital. Eleven more cases were confirmed, the last in October. No other cases have been confirmed either in the Guanacaste province or in the rest of the country. Almost all the cases in the first generation in the counties of Liberia and La Cruz had contact with Liberia Hospital as source of infection and were linked to the index case. This suggests that transmission took place within Liberia Hospital.
As recommended by the XII Technical Advisory Group on Vaccine-Preventable Diseases (TAG) in Guatemala, it is necessary to monitor vaccination coverage by district and to characterize districts at high-risk for measles (coverage less than 90%). Viral isolation is required from all chains of transmission. An adequate sample of urine should be taken in sterile container at first contact (preferably within one week of rash onset) with suspected measles cases.
Source: Ministry of Health, Costa Rica.
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