Gordon Brown and Angela Merkel met in Berlin in July
The two leaders outlined an initiative to fight illnesses like HIV/AIDS and cut childhood and maternal mortality rates during talks in Downing Street.
They said an international health partnership to target overseas aid will be officially launched on 5 September.
This will improve access to health services in poorer nations, they added.
'Very clear'
Mrs Merkel's visit to the UK is her first since Mr Brown became prime minister nearly two months ago.
After a press conference, the two left for Wembley Stadium to watch England play Germany in a friendly football match.
The prime minister said that, although he was a Scot, he hoped England would win after scoring "a large number of goals".
Speaking after the talks, Mr Brown rejected trade union calls for a referendum on the EU treaty.
Mr Brown is facing calls from the Tories for a referendum on the treaty, which were echoed on Wednesday by the GMB and RMT trade unions.
They say the treaty is similar to the proposed EU constitution, which was abandoned after it was voted down in France and Holland.
You may recall it's not the first time these two have met as leaders...
BBC political correspondent Laura Kuenssberg
Read Laura's thoughts in full
An ICM poll earlier this week suggested 82% of British voters want a referendum on the treaty.
Among Labour voters the poll suggested the figure was 80% and for Tory voters it was 88%.
But Mr Brown said the "proper way" to discuss the issue was in parliament.
Shadow Europe Minister Mark Francois told the ePolitix.com website he would like Mr Brown to tell Mrs Merkel that public opinion was "running so high" he felt he had to hold a referendum.
But Europe Minister Jim Murphy said this was unnecessary because the government had made it "very clear in the treaty that the UK will not give away important areas of sovereignty to the European Union".
Afghanistan
Meanwhile, Liberal Democrat leader Sir Menzies Campbell called on Mr Brown to challenge Mrs Merkel over Germany's role in Afghanistan.
He said: "The prime minister should take this opportunity to impress upon Chancellor Merkel the overwhelming necessity to ensure that Nato forces win in Afghanistan.
"He should tell her that the chances of doing so are being materially damaged by the so-called 'caveats' which Germany has attached to the deployment of its force.
"These caveats detract from the effectiveness not only of the German troops, but of the Nato effort as a whole."
El Primer Ministro del Reino Unido Gordon Brown y la Canciller de Alemania Angela Merkel hicieron hoy un llamamiento para mejorar la salud en África – uno de los ocho Objetivos de Desarrollo del Milenio.

Los mandatarios del Reino Unido y Alemania pidieron más esfuerzos para mejorar la situación de VIH/SIDA, Malaria y otras epidemias que arrasan África.

Brown ha tomado la decisión en vista de un reporte que indica que es poco probable que se alcancen, para el 2015, los ocho objetivos del milenio – ocho cláusulas propuestas en 2000 para el 2015.

Es la primera visita de Merkel al Reino Unido desde que Brown asumió.

La reunión bilateral anunció la creación de una 'Asociación de Salud Internacional' que incluye a Gran Bretaña, Alemania, Canadá, Noruega y también al Banco Mundial y la Organización Mundial de la Salud.

=== Afganistán ===

Los mandatarios además hablaron sobre Afganistán.

El Reino Unido ha mostrado su descontento por la falta de tropas de miembros de la OTAN en Afganistán, y reprochó que sus tropas, junto con las de Estados Unidos, Países Bajos y Canadá, son las únicas en el área.

Alemania tiene tropas en el país, aunque limitadas y en un área del norte relativamente pacífica.

A esto, Merkel respondió que las tropas británicas y alemanas tienen "distintas responsabilidades, pero son parte de la misma misión".

Angela Merkel además anunció que seguiría hablando con Brown sobre el tema.