From 2003 to 2007, Italy is implementing a national plan to eliminate measles and congenital rubella . In addition to efforts to reach 95% coverage with the first MMR dose by the age of 24 months, ongoing activities include increasing coverage with the second dose at 5-6 years of age, and catch-up of 6-13 year old children in primary and lower secondary schools. In Toscana (often known in English as Tuscany - a region of central Italy with approximately 3.5 million inhabitants), coverage with the first measles-containing-vaccine dose by 24 months of age was 44% in 1993, 65% in 1998, and 89% in 2003 , according to three cluster sampling surveys. In 6-10 year old children attending primary school, MCV coverage was estimated to be 88% for the first dose, and 66% for the second dose by December 2004. Although the elimination plan has so far been very successful in achieving its goals, a continually insufficient coverage rate for measles vaccine during the past 15 years has created a large pool of susceptible adolescents and young adults.
Description of the outbreak
Between 20 January and 5 May 2006, 40 cases of measles were reported to the local health unit in the province of Grosseto in Toscana. The population of the province, which includes the town of Grosseto and the surrounding area, is approximately 200 000. Twenty three of the cases (58%) were in males and 17 (42%) in females. Seventy five percent of the cases occurred between mid-February and the end of March 2006, with a peak in March (Figure 1). Ninety five per cent of the patients were over 15 years old (Figure 2), and the mean age was 27 years.
The index case was a 23 year old woman who showed symptoms suggestive of measles after returning from a visit to India. She initially presented with fever, and was treated with antibiotics. She then developed a generalised rash, which was diagnosed as a drug reaction, and she was admitted to hospital in Grosseto on 20 January 2006. During her admission to hospital, she came into contact with a nursing student, who developed measles 14 days later, on 3 February 2006, and was the first secondary case to be reported.
As patients were not always properly isolated (for example, during transportation between different wards), 12 patients (30%) in this outbreak were thought to have acquired infection through nosocomial transmission. Eight of the cases (20%) were in healthcare workers.
Figure 1. Number of measles cases by week of onset. Grosseto, Toscana, Italy, 2006
Figure 2. Number of measles cases by age group, outbreak in Grosseto, Toscana, Italy, 2006
Twenty six cases (65%) were laboratory confirmed, (65%) were laboratory confirmed, while the remaining 14 were epidemiologically linked. Measles virus genotype D4 was confirmed in samples from seven patients. No biological samples for measles confirmation were collected from the first patient, the 23 year old woman who had returned from India, as samples should be taken within seven days of rash onset, and the diagnosis was too late. However, measles virus was isolated from the first secondary case and had the same genomic sequence as all the other cases.
Of the 40 patients, 14 were admitted to hospital (35%), including 8 of the 12 patients who acquired measles by nosocomial transmission, and 6 of the remaining 28 cases. Complications recorded in the hospitalised patients included cholestatic hepatitis with cytonecrosis (7 cases; 50%), thrombocytopaenia (2; 14%), respiratory distress (1 case; 7%), brain oedema (7%), otitis media (7%), haemorrhagic lesions (7%), bacteraemia with isolation of Streptococcus capitis, (7%), and candidiasis of the mouth (7%). None of the patients died.
Only one patient reported having received measles vaccination, in 1982.
Actions taken and conclusions
In response to the first secondary case, active tracing of contacts began on 6 February 2006, and MMR vaccination was administered to individuals who were not vaccinated or who had previously received only one dose of measles-containing vaccine. In total, 27 contacts were vaccinated: 26 received their first MMR dose, and one was vaccinated with the second dose. No further cases were reported after 5 May.
Measles virus genotype D4 has been found to circulate in India , and outbreaks related to importation of this genotype were recently reported in Europe [4-6]. In this outbreak, measles transmission following importation occurred in a hospital. A similar experience recently occurred in northern Italy, in the autonomous province of Bozen , where a cluster of five measles cases, three of which were related to nosocomial transmission, were reported. This underlines the importance of verifying immunity and offering MMR vaccination to susceptible healthcare workers.
A high rate of admission to hospital was also observed. This is expected when measles infection is acquired by adults, who are more vulnerable to severe complications.
It must be stressed that recognition of this outbreak was only possible thanks to the implementation of the elimination plan for measles and congenital rubella and to the efforts of healthcare workers to implement laboratory confirmation of cases. The outbreak was extremely showed that a system of early warning and laboratory confirmation is feasible in Toscana. It will be crucial to properly investigate all suspected measles cases as the goal of measles elimination approaches.