Ten of the signatories are South Africans. The rest are all prominent British, European, Australian or American members of the scientific community that concentrates almost exclusively on HIV and Aids.
Most of them attended the recent 16th international HIV/Aids conference in Toronto, Canada, where South Africa's "vegetable stall" was scathingly criticised.
"According to the best estimates of South African actuaries, more than 500 000 people without access to anti-retroviral medication have reached the stage of the HIV infection where they urgently need the medication to save their lives," the scientists wrote in the letter.
Manto is 'an embarrassment'
At the Toronto conference, several delegates, including UN special envoy on Aids Dr Stephen Lewis, sharply criticised Tshabalala-Msimang for South Africa's exhibition of foods as alternative to Aids medication.
"Garlic, beetroot and lemons are not alternatives to efficacious medication for the treatment of a specific viral infection, and to what follows it, in the human immune system," the letter says.
"Large parts of the impressive advances made in the field of HIV science come from scientists and doctors from South Africa and elsewhere on the continent."
"Their expertise ought to play a large role in alleviating the tragic consequences of the disease in South African society."
The letter adds that antiretrovirals are currently the only way to alleviate the consequences of HIV infection.
"The evidence supporting this statement, is overwhelming and indisputable."
The scientists ask directly for the immediate dismissal of Tshabalala-Msimang.
"We are deeply affected by the way that science is being undermined by the South African minister of health."
Before and during the 16th international Aids conference, Dr Tshabalala-Msimang expressed a pseudo-scientific attitude to the management of HIV infection.
"We insist on an end to the catastrophic, pseudo-scientific policy that portrays the South African government's reaction to HIV/Aids."
"Denying that HIV causes Aids is ridiculous against the background of scientific evidence. The promotion of an ineffectual, immoral policy on HIV and Aids puts human lives in danger."
"Having a person as minister of health who does not command international respect at all today, is an embarrassment for the South African government."
"The group of scientists include Professor David Baltimore of the California Institute of Technology, the 1975 Nobel Prize winner for Physiology of Medicine; Professor Quarraisha Abdool Karim, head of the Caprisa women and Aids programme at the University of KwaZulu-Natal; Professor Dennis Burton of the Schripps Research Institute in the US; and Professor Philipple Kourilsky, honorary president of the Pasteur Institute in France.
After the end of the international conference in Durban in 2000, about 5 000 scientists from various fields of specialisation signed a petition stating clearly that HIV does cause Aids.
At that conference, Mbeki said he doubted that HIV leads to Aids.
The scientists' letter quotes the chair of this year's Aids conference, Dr Mark Wainberg: "In Durban we expected the South African government to be on our side. Instead, we encountered a denier as president, who turned his back on us." Mbeki's spokesperson Mukoni Ratshitanga told Deon de Lange that the president received the letter. "But the president has not read it yet because of the state visit of President Putin of Russia."