The agency is also urging parents to make sure their children have both shots measles, mumps and rubella or MMR before they return to school.
So far there have been 480 confirmed cases of measles in the United Kingdom in 2007, the federal agency said. That compares with a provisional total of 756 cases last year, the highest number recorded since current monitoring began in 1995.
The HPA said it is receiving more samples each day, with about half of them testing positive.
Expressing her concerns over the rise in the number of cases, HPA immunization expert Dr. Mary Ramsay told the BBC: "We've been very worried because the cases have stayed up over the summer holidays."
"We hadn't had any deaths from measles since the early 1990s, but unfortunately we had one death last year and we don't want any more," she added.
Measles, also called rubella, is a highly contagious - but rare - respiratory infection that's caused by a virus. It causes a total-body skin rash and flu-like symptoms, including a fever, cough, and runny nose.
Since measles is caused by a virus, symptoms typically go away on their own without medical treatment once the virus has run its course. But a child who is sick should be sure to receive plenty of fluids and rest, and kept from spreading the infection to others.
The MMR jab is used to immunise children against the disease. The vaccination rates using the MMR saw a rapid decline after claims made in 1998 that the vaccine was linked to autism.
However, no such research has proved that MMR vaccination is linked to autism. The latest figures show that 88 percent of UK children begin school having had one dose of MMR.
Health experts warn that unless approximately 95 percent of a population is vaccinated, measles outbreaks are likely.
